Net equity 4200€, single-family house for 500k, 25% equity financeable?

I would say the financing is probably fine, that you can finance the amount. For peace of mind, I would still keep a household budget once. I see the critical point more at Würzburg, the houses there are rather available for €600,000, if there are any that fit at all. It will more likely be a wider area around Würzburg...

I can only agree with the previous speakers. Good creditworthiness, sufficient equity, good concept. However, I would advise against using the parental home as collateral unless it is absolutely necessary. There are some mortgage lenders who forgo such "lifelines." If you want to have the house paid off in 30-35 years, you should consider a full repayment loan with an interest rate fixed for 30-35 years. This way, you have interest rate security down to the last cent and are not dependent on a potentially expensive refinancing in 20 years. (30 years fixed interest full repayment at 1.50% interest or 35 years fixed interest full repayment at 1.60% interest possible)