realistic cost planning

Hello dear home builders, we are currently planning to build a house. It is still uncertain whether it will be a prefabricated house or solid construction. We will only be able to contribute "cosmetic work" as labor ---> so it will probably come down to turnkey or one stage before that. The following facts are on the table. - Building plot 500-750 sqm (currently not available, estimated costs 75,000 EUR). - No basement - Living area 140 sqm - Double garage (with storage space as basement replacement) In terms of quality, we expect it to be a decent good (average) quality but we do not want luxury equipment =). Since we unfortunately do not have a plot, we have repeatedly not received an offer from a prefabricated house company. However, since we first want to make a cost plan and then buy a plot if the result is positive, a cost planning is urgently needed. Therefore, we would be interested in your estimates/experiences regarding the following items: Building plot: 75,000 EUR House: ? Garage: ? Additional construction costs: ? Outdoor facilities: ? Furniture/Kitchen: Total costs: ? What do you think, solid construction or prefabricated house? How do they differ in price? Thank you very much for your answers

Building plot: 75,000 EUR
House: 230 K€
Garage: 15 K€
Additional construction costs: 30 K€
Outdoor facilities: 15 K€
Furniture/Kitchen: 15 K€
Total costs: 380 K€ + 20 K€ buffer ==> 400 K€

I have no expert knowledge, but this is my estimate for turnkey including flooring and painting.

What kind of furniture do you need!? So far we have spent 7,500€ on furniture, lamps, etc. and are not done yet. But we came from a 70 sqm rental apartment – meaning that the 15 K€ item assumes that you have furniture and maybe just need a bit here and there.

We currently live in an 85sqm apartment, so we have some furniture but will definitely need others. Especially the kitchen, which makes the whole thing more expensive... Do you think the cost for a solid house or a prefab house? We recently had an appointment at the bank and they estimated the cost at €444,000. We were really shocked by this price and it would be too expensive for us.

Prefab houses are somewhat more expensive in the single-family house sector of this size.

Massive - prefabricated house I have even less knowledge about.
What would be affordable for you? x * 0.05 / 12 = monthly rate --> x = loan amount
e.g. 1400 € / 0.05 * 12 = 336,000 loan + equity = maximum house price

We do not want to pay off the house for more than 20 years, therefore we do not want to spend more than 400000 € in total.