Looking for affordable & good prefab house providers. (lower budget)

Try Town & Country, e.g. house type "Raumwunder 100". That should be doable in the standard version for about 180,000€.

I would like to add the following for the original poster: It may be possible to put up a house in the standard version for 180,000 euros. But here, additional costs, outdoor facilities, often even the foundation slab and earthworks (the biggest cost drivers), possibly carport/garage, floor coverings and painting work, and of course kitchen and furniture, still come on top. And unfortunately, none of this can be had for 20,000 to 40,000 euros, as the budget would be used up by then (assuming one can even find a plot for 100,000 euros including incidental acquisition costs, which is also not certain).

Kitchen and furniture are out. Available on classifieds for free after dismantling. You have to think like that for it to fit.

For a detached single-family house, that will not be enough, for a terraced house probably yes.

Because 400 m2 of land is really not that much, and if you take a terraced house instead, you just miss one side to walk around. So what! Take a look at projects in your area without prejudice, for example Deutsche Reihenhaus has several projects in BW. Depending on the area, the budget should then be sufficient for a nice 130 m2 instead of struggling endlessly and painfully for an unattractive 100 m2. Such a thing should also be less stressful and more plannable.

I would look at garden houses or log cabins. You can get a lot for the budget there.

I would look at garden houses or log cabins. You can get a lot for the budget there

Party tents are even a bit cheaper, but they would probably also fail due to the energy saving ordinance....

With the budget, you cannot build a single-family house in BW. Even a terraced house from BT will not be possible in the desired location (250€/m² land).