Is financing feasible or are we overextending ourselves?

Yes, but you start the thread with completely different assumptions. Of course, if you get everything for free, as a gift, or "for a crate of beer," then that's great and somehow it will become a house. Maybe you should have mentioned this small but not unimportant detail at the beginning.

At the beginning, I simply wanted to know whether we can manage with the targeted rate and our income, or whether the ratio is okay. The discussion just developed into the project. And then I also put all the details on the table.

I simply wasn't sure how many details about the house you needed. ^^ but yes, you're right. More details from the start would have been better.

Well, there’s little for free. But a lot of work can be done by ourselves and the construction will be very flexible.

For me, the only question is whether you have enough time? Time in general for the EL and time or money for a possible double burden. Do you have an electrical specialist company that approves the EL? Electrical work in EL takes time and is not a gift. Chasing, pulling cables, installing boxes, and planning. You urgently need to keep the effort in mind. Otherwise, the conditions are ideal. Excavator for free, etc., saves a huge amount of money.

We have €500 less income and need to finance about €310k (Equity: €140k). To be honest, I hardly want to finance any more. Therefore, if I were you, I probably wouldn’t do it and would save for a while longer.

Excavators for free, etc. saves a huge amount of money

Here I think I have to put things into perspective. For the shell construction excavation etc., meaning the excavator from the construction company, we will have to pay. I can't just put a foreign excavator in front of the construction company.

Later on, for gardening, landscaping, etc., we might get one like that.

Well, ideally the conditions would be with a bit more budget. ^^ but without contacts and personal effort it wouldn't be possible at all. This way it might be possible, at least.

For me, the only question is whether you have enough time? Time in general for the EL and time or money for a possible double burden.

We "have to" make time. There is no alternative. We are both aware that it will be very exhausting and have talked about it often and frequently.

We are not alone in this. We have enough helpers. My dad and father-in-law both built their own houses and accordingly have some experience. In addition, I have 3 very good friends I can rely on.

If we don't take the time, the dream of home ownership will burst one way or another.

We have 500€ less income and need to finance about 310k€ (equity: 140k€). To be honest, I hardly want to finance more. Therefore, if I were you, I probably wouldn’t do it and would save for a while longer.

Thanks for the input. Before we sign anything (the property is notarized and reserved), we will definitely go through all the numbers and expenses of the past months again. The 500 euros in income should correspond quite exactly, as an additional installment, to what we want to finance more (rather a bit less). The remaining amount should therefore be similar to yours. (assuming one had the same fixed costs and term)

I point this out because I have two friends in my circle who were built similarly. But with even more EL. Construction helpers always came from the circle of friends. You have to be able to rely on them 100%. And for a good year. Every Saturday you will have to use them. When others want to do something in the evening, you will be working and/or planning.

I renovated myself. With a lot of EL. That is EXTREMELY exhausting. Not only for you, but also for the family. You have to be absolutely aware of that.

Your dad has connections to the GU. Ask him about a modular system. The excavation pit, for example, can be done yourself. Trenches for the sewer connections, construction road, etc. Ask how flexible he is.

Your trump card is the relatives in expensive trades. If you look at material prices for plumbing and electrical work, it’s a joke compared to the prices charged by companies. Underfloor heating, WP, cables, etc. are low in price. The companies charge for the work and the expertise.