Hello,
I started by editing your post to make it readable
The plot we want to buy is taken from an existing parcel and is up for sale. Size approx. 500m², rectangular and sufficient for us. There are currently garages on the site, which will be completely removed by the owner. At the same time, the driveway will also be removed. So we get the plot at ground level. The surveying will also be done by the seller. Up to this point, everything is fine.
Here you should not assume that this completes the entire surveying for the building project. The seller will "only" pay for the parceling or subdivision survey. This means that a further €2,800.00 - €3,200.00 (depending on the surveyor) for the actual house construction including the final measurement is still due.
1) There is no development plan! Is something like this problematic or will the developer apply for this at the office during the house construction?
That is not a problem, you must then build according to §34. That means according to the surrounding buildings. If mostly single-story detached houses are built in the immediate vicinity, you will have to build likewise. If you have special requirements for the roof shape and this is not found in the immediate vicinity of the plot, you can forget about it. So the roof must also adapt to the surrounding buildings.
3) Since we want to build with a basement and all houses around the plot have basements, do I still have to get a soil survey?
Anyone who builds without a soil survey is playing with their existence; regardless of whether neighbors have built with or without one. In addition, a soil survey is needed, among other things, so that the excavation contractor knows how to, for example, slope the excavation pit.
4) What else must we consider that we have forgotten?
You have not yet had a consultation regarding the building project? Then read carefully here in the forum! Contrary to your initial statement, all topics that should interest you are indeed covered here. But you have to read yourself
The plot costs €124,500 ... additional costs such as notary, property transfer tax, etc. will be added ... We do not need a showpiece and have set a limit of approx. €320,000 +- €20,000. All furniture is already available and we even have a kitchen if needed. We want to build as soon as possible
First of all, you should take a look at this:
https://www.hausbau-forum.de/ratgeber/bauherrenhilfe.422/bauherrenhilfe-vor-vertragsabschluss.424/bausumme.662/#Baunebenkosten%20und%20Grunderwerbsteuer
Depending on the federal state and deviations, this list applies nationwide; I based it primarily on the costs for NRW.
Now let’s calculate based on 120 sqm living space plus usable basement and a budget of €340,000
Budget: €340,000
Plot: €124,500
Single-family house 120 sqm/Living space/KfW 70: €186,000 (single-story detached house without major frills)
Usable basement: €38,000
Additional construction costs: €35,000–40,000
Painting work by subcontractor: €10,000
Floor coverings by subcontractor: €10,000
Outdoor facilities by subcontractor: €10,000
Carport or prefabricated garage 3 x 6: €6,000
Reserves extras: €10,000
All in all, this results in an underfunding of €94,500
The users who estimated costs of €400,000 plus "x" are thus quite accurate with their assumption. AND – with the above numbers, there must be no surprises in the ground (soil replacement), otherwise another €8,000–10,000 may easily be added.
If you forgo the basement – which I strongly recommend given your desired budget – you must underpin the neighbor’s basement, founding on soil level under the neighbor’s basement. This requires stepped underpinning and, depending on the soil report requirements regarding execution, will cost you between €8,000–10,000. This means you would save €28,000 if you waive the basement. However, you will probably need a longer prefabricated garage, which costs €12,000 including required strip foundations. Realistically, you would thus save about €22,000 by foregoing the usable basement. Still a lot of money, but even with these measures your desired budget will be exceeded. Have you already consulted an independent financing broker and discussed your financial situation with him?
Rhine-region greetings