How much equity is needed for home purchase financing?

The KFW can often be redeemed early with special repayments, then that would no longer be in the way.

Those times are long gone. There is always a cancellation fee.

The times are long gone. There is always a VE.

Well, we do not want to repay the KFW prematurely but start repaying after the interest fixation period of 5 years, we only want to start repaying after 3 years then the apartment will be paid off without any remaining debt and we would have roughly 500 euros more per month from the rental to repay the KfW We could also sell after 5 years, repay KfW and use the remaining amount to pay the final installment

There have already been tax mistakes made in the past. A rented apartment should never be paid off before the owner-occupied one. However, it counts as equity but is only useful if financed with the same bank. If you subtract the ancillary costs from the 15% equity, it is almost a 100% financing. Whether you sell the apartment now, in 3 years, or not at all, can be discussed when more facts are available.

How much equity do you have for the house financing?

20% (including cash, free land portions of the condominium, EL and all subsidy grants) of the total costs

How much equity do you have in the house financing?

That is almost secondary.
Much more important is the future percentage share of the monthly payment (with proper repayment) of the total income.

That is almost secondary.
Much more important is the future percentage share of the monthly payment (with proper amortization) of the total income.

Well, without the necessary capital, you lack the room to fill the bubble air. Only if you can do that will the bank discuss the next step with you. You then need a burden of a maximum of 33%-40% of the monthly household income.