Separate the single-family house with a granny flat again

Hello, I would like to separate my single-family house (200 sqm living space, including 50 sqm granny flat) again. There would then be an apartment of about 100 sqm on the ground floor, the granny flat of about 50 sqm, and a new apartment of just under 50 sqm on the upper floor.

Structurally quite easy to do. But is it that simple from a building law perspective? The ground floor and the granny flat are to be rented out. I would live in the new small apartment....

Do you really want to live in the small apartment yourself? I would think twice about that. Because on the one hand, it's simply more pleasant in a larger apartment, and small apartments are usually 1-3 room apartments that are ideal for renting out. That means often/always occupied and the price/performance ratio is also the best.

From a building law perspective, there shouldn't be any major problems. Taxes will probably be due again and sewage separately (presumably), but it should be doable. You would have to ask at the municipality/city. Here in town, a few have already done this for student apartments.

But is that really that simple in terms of building regulations?

You don't have to ask an anonymous forum, but the building authority responsible for you.

Rhenish greetings