Building a house with a granny flat financially realistic?

The plot is 600 sqm. The sqm prices here are 80 euros per sqm. The house should be about 120 plus 60 sqm in size.

180 m2 plus ancillary construction costs are from 400 TE on a top-level plot. Only if your husband has all trades at hand and is on a brotherhood basis with all of them (so that they practically slave for him for free) could the 300 TE mentioned above perhaps be scratched. So, with still a lot of own labor, rather 350 TE would be feasible.

That would always be without exterior work, without basement, without kitchen, without garage. With land at 50 TE on top, we come to at least 400 TE building sum – with zero equity and 1000 euros free plus 500 rent, I find that already very shaky.

The KfW would give you 5 TE per apartment for a KfW Efficiency House 55. If the house builder achieves that as well, no problem. If it costs extra, you just have to recalculate, but with the building sum, 2x 5 TE are also peanuts. Otherwise, with the KFW 153 program, there are 100 TE as a loan, which is usually less favorable than at the bank (somewhat higher interest and only 10 years term) but ranks second in the land register. This way you can get the main loan itself cheaper.

I clearly see a NO here. Too little equity, too little income, too big wishes - that won't work.

Can the parents give a gift and then pay less rent? That would also have the advantage that you can deduct more from the tax office. I don't know how securely the rent from relatives is calculated, with unrelated tenants no bank agrees under the conditions. If yes, then definitely 2 separate financings for own apartment and granny flat.

My parents cannot contribute anything (yet). My mother will inherit a lot and will then finance part of the house. Of course, no one knows when that will be. I know that you don’t get a grant from the KfW. That is why I also wrote funding. Suitable houses have currently not existed here or for the past 2-3 years anyway. Otherwise, we would buy one.

The subsidy is simply a loan, just like the one from the bank. It doesn't have to have better conditions, it can even be worse. It does not affect your construction project, whether with [KfW] or without.

I also think a lot doesn’t fit. I don’t even see a single-family house without a granny flat... And that’s because a) the equity would have to cover the ancillary purchase costs. And because you would have to borrow too much money given your salary. Maybe some things are feasible if the mom can actually put money into the house construction. But that remains to be seen for now.

So someone who doesn’t necessarily want to make money from it.

With the current interest rate, you are still the winner. Banks offer free advice. And that’s what I would also advise you: simply talk to your house bank. But don’t let them push a building savings contract on you without checking such a thing.