Purchase of land with existing building; new construction planned in the future

Hello dear community,

we will soon purchase a plot of land with a vacant house (approx. from the 50s/60s) and are planning a new building in the medium term.
Now the plot needs to remain unused for about 2-5 years for further accumulation of equity and due to my wife's professional situation (currently parental leave, a permanent position is required for the loan).
I have some questions about this and would appreciate your experiences and tips.

(1) Demolish the house immediately or leave it vacant: What are the risks and obligations if I demolish the house immediately or leave it standing? Which factors should I consider? How would you proceed?
(2) Under what conditions could one consider renting out such an old house again? (with manageable renovation) My logical common sense tells me that this would cause more stress than benefits: maintenance obligations, energy certificate, new heating system, termination in case of new building, etc.
(3) If I demolish the house immediately, how do I deal with the basement? We want to build without a basement. Would the pit be filled with F1 sand and compacted? (The new building will also be significantly larger than the existing one)
(4) Could it make sense after demolition to install a permanent construction water connection right away? Background: If the water line remains unused for >1 year, it is removed in our district and I would have to pay >€10k again for the street tapping at the new building.
(5) Related to (4): Is it possible to establish a long-term construction power connection? This would be necessary to heat the construction water connection in winter and have electricity on the plot if needed. With the classic rental of construction power boxes with monthly inspection, costs would probably explode. Are there alternatives?
(6) Realizing cost savings in house construction through a long planning horizon? What possibilities do I have to realize cost savings for the new building through a long planning horizon? Are there any tips on how I can somehow use this unfavorable situation to my advantage?
(7) Use / monetize the undeveloped plot sensibly somehow? Are there possibilities to use or even monetize the undeveloped plot in the meantime? In case of available construction power/water, one could consider using and possibly even leasing the garden?

Thank you in advance for your help and tips!

(1) Tear down the house immediately or leave it empty: What are the risks and obligations if I tear down the house immediately or leave it standing? What factors should I consider? How would you proceed?

You could write entire novels about this. Consider: insurance, property tax (if you tear it down, check the property tax for an undeveloped lot for the next five years), possible vandalism.

(2) Under what conditions could one consider renting out such an old house again? (with manageable renovation) My common sense tells me that this causes more stress than benefits: obligation to renovate, energy certificate, new heating system, termination in case of new construction, etc.

Depends on what would have to be done. Renovation obligation is relative – read up on what MUST be done. And then keep in mind that if something must be done, you have two years for it.
Oh yes, nobody comes to check. Not that I want to encourage doing nothing at all, but that is the norm. Energy certificate? So what. No plaintiff, no judge. Apart from that, producing it online takes about 5-10 minutes for a very small fee. Meaningfulness? None, like with many energy certificates. Termination due to new construction? Nope. Just make a fixed-term rental contract for two years initially. Then the issue is settled after two years and you can rent out again if necessary.

(3) If I tear down the house immediately, how do I deal with the basement? We want to build without a basement. Would one fill the pit with F1 sand and compact it? (The new build is also significantly larger than the existing building)

You will know that once you know the planning of the new build.

(4) Could it make sense to set up a permanent construction water connection immediately after demolition? Background: If the water pipe lies fallow for more than a year, it is dismantled in our district and I would have to pay >10,000€ again for the road borehole at the new build.

Depends on the costs of the construction water connection. Apart from that, new water lines have to be laid anyway for your new build, or am I misremembering your project? For example, we had a well drilled for our build (600€) since we wanted it anyway for the garden. Think outside the box – maybe something like that could work for you too?

(5) Related to (4): Is it possible to set up a long-term construction power connection? This would be necessary to heat the construction water connection in winter and have power on site if needed. Renting the construction power boxes in the usual way with monthly inspection would likely explode the costs. Are there alternatives?

Buy a construction power box yourself on classified ads. Whether construction power is possible for that long without use, you have to inquire. Regarding points 4) and 5), I would worry about vandalism over several years. I would NOT leave both connections unused on the property for years.

(6) Realizing cost savings in house construction through a long planning horizon? What possibilities do I have to realize cost savings on the new build through a long planning horizon? Are there any tips on how I can somehow sensibly use this unfavorable situation for myself?

How about realizing cost increases through a long planning horizon? You cannot optimize so much over the years that it will compensate for the continuously rising construction costs. Sorry, waiting long gets more expensive, not cheaper...

(7) Using / monetizing undeveloped land somehow sensibly? Are there ways to sensibly use or even monetize the undeveloped land in the meantime? If construction power / water is available, one could think about use and possibly even leasing of the garden?

Use it to park trailers, caravans, etc. Farmers around here do that with their old barns and parking areas on their farms. But it costs you insurance. Otherwise, think about who might need land for a certain time. I can’t think of anything else. Normally, a developed (and not rented) or undeveloped lot simply costs money over time and yields no income.

Thank you very much for the quick response. I am not too worried about vandalism for now, as the location is in a quiet dead-end street with no through traffic or occasional traffic.

It depends on the costs of the construction water connection. Apart from that, water will have to be newly installed anyway for your new building, or do I have your project wrong in mind? For example, we had a well drilled for our construction (€600), as we wanted it for the garden anyway. Think outside the box - maybe something like that is possible for you too?

Buy the construction power box yourself from classifieds. Whether construction power is possible for that long without use, you have to inquire.
Regarding points 4) and 5), I would be concerned over several years that vandalism could become a problem. I would NOT leave both connections unused on the property for years.

From everything I could find out, we could reuse the existing connection from the old building (relatively new piping) for construction water and then for the new building afterwards. However, if we leave the line unused, we are forced to make a new connection from the street after >12 months... Accordingly, the detour via construction water (possibly for garden irrigation) and then after a few years the use for the new building.

How about accepting cost increases due to the long planning horizon? You can’t optimize enough over the years to compensate for the ever-rising construction costs. Sorry, waiting longer will be more expensive, not cheaper...

Yes, I feel the same. Especially since we will have no entitlement to subsidies in 2–5 years. However, the overall project is currently too risky for me to tackle it directly. Our family planning is now complete, and in the next few years there will again be the possibility to rely on at least 1.5 incomes (instead of 1) and to start paying off part of the property.

At first, I don’t worry too much about vandalism since the location is in a quiet dead-end with no through traffic or occasional traffic.

Ideal location for vandalism. If the house is still standing, it makes a good hangout spot for a youth gang.
Actually, vacant houses are the absolute norm. Just think about how many old shacks in the Ruhr area stand empty that nobody wants or that are uninhabitable.

Yes, I feel the same way. Especially since in 2-5 years we will no longer have any entitlement to subsidies.

I’m absolutely sure that you will still be subsidized in 2-5 years. At least for very climate-friendly new construction – in whatever form.

I am not worrying too much about vandalism for now,

But yes, you are planning some (demolition of an existing building, of which you report no "disadvantages" except a gifted basement).

Now the property has to remain idle for about 2-5 years for further savings of equity and due to my wife's professional situation (currently parental leave, permanent employment is required for the loan).

Saving equity for demolition and additional costs, despite parental leave = additional need recipient already in the world. Some days I wonder several times how many shots some people fail to hear.

Yes, you are planning one (demolition of an existing building, from which you report no "disadvantages" except for a gifted basement).

Just because I don’t mention the disadvantages here doesn’t mean they don’t exist.
The house is old, worn out and without substance, I can’t stand up in the basement because of the height, it is damp, the house has a footprint of max. 60-70 sqm (there are five of us) etc. etc.; a renovation is simply out of the question here. It’s no coincidence that I wonder whether the house can still be rented out somehow or if it’s even allowed to rent it out at all.

Saving equity for demolition and further additional costs, despite parental leave = increased needs carrier already in the world. On some days, I ask myself several times how many shots some people cannot hear.

I think everyone can best assess the situation for themselves. I have a pretty clear overview of how much surplus we generate (despite children). It should be clear that the situation will be somewhat more relaxed once another 2-3 annual bonuses have come in and my wife has an income again that can be planned. But I am also aware that we have not gained anything if we experience similar price increases as in 2021/22 again.