Construction planning phase - When to start?

My girlfriend (soon to be wife and yes, she knows about it too) and I are both employed in the public sector. So far, there are no children yet, but looking to the future, it should be 2, maybe even 3. A little bit always depends on the money, and therefore it directly depends on the house as well, apart from the number of rooms... but let's start from the beginning.

We have already bought a plot of land. It is located in Fredersdorf (15370), near Berlin (30-45 minutes to the city center). The size is 840 sqm and the floor area ratio is supposed to be 0.25... "supposed to be," because when looking at surrounding properties, one might start to wonder. So far so good, this is a plot in a developed residential area, so not a pure building site. The plot is free from developers. The purchase price was €85,000 although the standard land value is €70/m². Accordingly, the financing looked like this: €59,000 real estate loan, €1,000 equity, and €25,000 private loan with special repayment rights. Now please don’t go into motherly advice. We knew what we were doing. Hence the little note to you with "special repayment rights." The price was high for our feeling, but justified and, very importantly, affordable. It had previously been used as a weekend plot. On it stands a very well-preserved bungalow of 30 sqm with partial basement and another 30 sqm ... enclosed porch? Conservatory? Hallway-like porch with conservatory character??? It’s hard to describe. In any case, dry, wind-protected, uninsulated, locked, and tiled. The bungalow itself is insulated and has double-glazed windows. Definitely not what I would consider a typical DDR bungalow. The bungalow is located in the front third of the plot. Wastewater is connected to the bungalow and drinking water is currently in the commissioning phase. Electricity and telephone are, of course, already connected. Only gas is "only" connected at the street side. As for the plot itself, it is botanically diverse and well-kept. Fence, hedges, pond... the whole program is here. The dimensions of the plot are approximately 18 m x 47 m.

Now to the actual point. I would like to know how you assess where this could be heading for us and whether it matches our (desired) expectations. Wishes in such matters are often also a negative indicator. Therefore, the opinion of uninvolved third parties with experience reportoire can help, in my opinion. I try to give as much insight as possible. But don’t complain right away if I forget something. If I can, I will send it afterwards.

The two of us are secured in the public sector (No, not civil servants, we are regular employees). Net income is €3,700 together. In the short term, the journey is heading toward €4,000. Currently, we pay €400/month for the plot - the fastest possible repayment is currently planned. Each of us can currently put aside €600-700 per month. A monthly rate later should be €1,000 - €1,200 plus additional costs.

Regarding the house and the associated ideas: it should be a townhouse with 120 - 130 sqm. The built-up area CAN be up to 10 x 10 m with compliance to the setback requirements. Later I will upload a sketch for this - technically not possible at the moment. Construction should be done with one type of brick... preferably sand-lime brick. Our wishes are underfloor heating, cooking island, smart home, fireplace, walk-in closet, basement. Basement and cooking island are dispensable. Possible own contributions: basement waterproofing, gas-water installation, electrical installation, floors, and painting work, done by suitable family personnel. Additional costs due to the use of existing connections on the plot should be limited. For example, the plan is to route the drinking water connection, which is to be installed in the bungalow’s basement, out again behind the water meter and lay it frost-free at 1.30 m depth to the rear part of the plot.

Questions:
1. Are there missing details for all the questions below?
2. Is our plan realistic so far, or are we looking through rose-colored glasses?
3. What is a sensible approach to plan everything further from a construction technology perspective?
4. What could be a possible timeframe / what should one roughly expect?

Sorry if this last part sounds choppy, unfortunately it is due to my circumstances of unplanned stage-wise writing.

Is it building land? Is there a development plan?

No development plan. Development possible according to § 34 Building Code

Aunt Edit(h): I knew I forgot something... and it certainly won't end there either

Are there many urban villas with 30° hipped roofs in the neighborhood?

First, clarify the planning status of your property. According to the land use ordinance, the construction of a holiday home may indicate a classification as a small settlement area (§2) or as a special area (§10). For example, the size of the bungalow of 30m2 suggests this.

If this is the case, it remains to be examined whether construction of a residential building is permitted. You can best clarify this and other building and planning law questions in cooperation with an architect, who, as part of a so-called building inquiry (BVA), before the actual building application, determines the principle permissibility of the construction project with the building and, if applicable, other authorities, e.g., the Lower Landscape Authority or the Lower Water Authority. The BVA is then regularly necessary if there is no development plan, but the permissibility of the construction project according to §34 of the Building Code must be clarified. A preliminary draft of the house including a cost estimate can then also be part of the building inquiry.

Are there many urban villas with 30° hipped roofs in the neighborhood?

Many is exaggerated but here and there some are always standing.

First clarify the planning law status of your property. According to the Building Use Ordinance, the development with a holiday home may indicate a classification as a small settlement area (§2) or as a special area (§10). For example, the size of the bungalow of 30m2 suggests this.

If that is the case, it remains to be checked whether development with a residential house is permitted. You best clarify this and other construction and planning law questions together with an architect, who, within the framework of a so-called building inquiry (BVA), clarifies the principle permissibility of the construction project with the building and possibly other authorities, e.g. the lower landscape authority or the lower water authority, before the actual building application. The BVA is usually necessary when there is no local development plan, but the admissibility of the building project must be clarified according to §34 Building Code. A preliminary draft of the house including a cost estimate can also be part of the building inquiry.

So, it’s no longer a small garden settlement area. But the idea would certainly be funny. Before reunification, this was mostly settled with weekend plots. Meanwhile, this is the exception.

I had already asked the building authority in advance by phone how it looks. In principle, from the basic idea, it should not be a problem to build in the second row on this property. I am aware of the content value behind a telephone inquiry. Nothing can be established on that basis.