1. The prepayment penalty is NOT determined by the possibility of how the bank can now re-lend the money. A reinvestment interest rate (published by the Bundesbank) is applied. It should still be very low at 1% interest (depending on the remaining term). 2. Capital gains tax never applies on a sale if it has always been owner-occupied. Not after 6 months, three years, or however long. 3. If there are €470k left for a new property, between 10 and 12% additional purchase costs will apply. So, in doubt, €420k purchase price remains. Since it is an old building, probably still tens of thousands of euros will be spent for new paint on the walls, the new kitchen, and a few little things. It will therefore be a significant downgrade from the current property. If desired, then it is okay. 4. Renting out and renting anew will be absolutely not interesting from a tax perspective. With 1% interest and the low loan, there are no significant advertising costs remaining. A considerable chunk of tax will definitely have to be paid on the rent. (For example, rent €1,200 monthly = €14.4k annually. With €2,250 interest + depreciation on the house (€3k p.a.?) and a few other advertising costs, a surplus of about €7k remains. Then 25-30% tax on that is not really lucrative – especially if for the new house maybe also €14.4k p.a. rent has to be paid). 5. Almost every bank lets you take the loan with you if the value of the new house fits the financing and risk position of the bank. Just ask the bank.