Single-family house with granny flat - Which company to build with?

The plot measures 22m x 120m and is completely level building ground. However, a white tank is required for the basement (if we decide to have one). The development plan does not specify any restrictions. We would like to build a house with a gable roof (approx. 30° pitch). Each residential unit is intended to have a separate entrance. The granny flat should be about 50 m2 in size. It will include a bedroom, bathroom, kitchen with storage room, and living and dining area. The remaining apartment should be about 130 m2. On the ground floor, a guest WC, kitchen with storage room, and living and dining room are planned. On the upper floor, there is the bedroom with dressing room, two children's rooms, and a family bathroom. A carport is to be included in the planning. A small terrace is planned at the granny flat and one at the main apartment. This will be done by owner participation.

The construction budget without the land was planned at €300,000, although various providers (strangely also Living Haus) assured us that our budget was far too small.

Thank you very much for the first information

That is enough for us in the north for a 130-150 sqm house including incidental construction costs...

The plot is 22m x 120m and is completely level building ground. However, a white bathtub is required for the basement (if we decide to have one).

....Without basement

So 180 m2. Also from around 300 TE with rather simple equipment, upwards open. Plus additional costs (connections, permits, earthworks, drainage, cistern, etc.) of at least 30 TE (often significantly more, you only know more with a soil survey and concrete offers) and maybe 20 TE for the slab. I would forget about a basement right away.

A carport is to be planned. The terrace will be a small one at the granny flat and one at the main apartment. However, this will be done by own work.

Plus driveway, fence and entrance platform. All of that also costs material and machinery!

So you need at least 50 TE more for the size, better 100 TE. And you still have to be able to say "no" very, very often during construction and specification. So gas boiler, simple roller shutters, no corner windows, no laundry chute, nothing from Villeroy & Boch, simple tiles, etc.

Do you already have a soil survey or can you interrogate the neighbors regarding this?

Without basement + 30000 compensation area for utility room and storage room...

300k€ with a basement?!? Never, no way! I’m currently building 139sqm with a WU basement and there’s easily a 4..k€ in front of that, and that’s without a granny flat.

Okay, then thank you very much in advance! We are currently having a quote prepared from Massa Haus for the Lifestyle 34 without a basement for just over €110,000 as a shell construction. This should be possible purely based on the invoices, right? Loan €300,000 + equity €50,000 for additional construction costs