The idea of the house. Financeable?

Hello everyone, I have an idea to build a house but I am just wondering if it is feasible and what options are available.
798m2 plot with double garage is available.
No cash or building savings contracts.
We are 5 people.
The dream is a house that can later be divided into 2 when the children have moved out. No basement. We have sewage on the property but unfortunately a pumping system needs to be installed there.
What costs do we have there?
The front door wood stone masonry or prefabricated house does not matter as long as it is energy efficient.

Without concrete information about your economic situation as well as your wishes for the house, no one can really give you an answer. If you only have 1,500 EUR net monthly, you can't finance anything anyway. With 10,000 EUR net monthly, you wouldn't need to ask the question... House with 120 sqm or preferably 300 sqm living space? What is the value of the plot? Energy-efficient is also relative.

The property has an approximate value of 145K€ plus garage of 25K€ built last year self-financed.

House we should manage with about 120-160 m² rather small and mine.

Income 2500€ net

Supplementary electricity is available on the property. The electrical system. Could be completely done by oneself, as well as gas and water installation.

Apart from the fact that I think you are approaching the matter relatively "naively" (very very poor information/ideas about the house), I think that 2500,- EUR net as a family income (including child benefits?) for 5 people is rather very low. How much rent do you currently pay? Any loans? One income or does the wife also work? How old are the children? Any more children planned? Secure job?

Oh, child benefit of 521€ is added on top. And no more children are planned. A secure job is available. The scant information about the house is because I believe it should be affordable and not cover wishes. Rent currently cold 750€.