Financing evaluation. Specify total equity to the bank?

Thank you. So I’m not completely alone with the idea after all.

And as I said: Even assuming there would be a 50% market crash in 3 months, wouldn’t it be reasonable to just sit it out and then break even after 10 years? In parallel, in case of job loss, one could cover the ongoing annuities.

But as I said: I’m happy to be enlightened by you about the weaknesses of this construct.

You really have all the trump cards in your hand. There is certainly still potential for cost reduction in the execution for the house. And you can mix many options. Go to a financial advisor and to the bank. Then you have to consider how much optimization you actually want to do. Is it about the last tenth of interest and return? Or do you want to have the house and ETF assets until retirement and be basically satisfied with that?

Otherwise, just take a look at an offer with 20-25 years fixed interest rate, with around 3% repayment. That should certainly be feasible with your income. A monthly rate of €2000 - €2300 is doable. After 20 years there will be an amount X left – which you then have to finance or pay off accordingly.

The remaining amount after 20 years would probably be about the value of your apartment, so ultimately no big deal for you. Ask the advisor about the interest rate jumps, i.e., how much equity leads to a meaningful interest reduction. Then look at what that really means over 20 years – meaning, how high are the saved interest costs in euros. For example, if you save €15,000 in 20 years for €80,000 more equity in the financing, you can consider whether to realize this or rather invest the €80,000 over 20 years. If it goes well, you’ll have kept the €80,000 and earned more than the €15,000 saved. If not – you have to close the gap in another way. It’s and remains a gamble, and if there were no risk, everyone would do it.

So I would look at how much equity should minimally go into the house in a reasonable way. Then you can see if you can incorporate the apartment as collateral to already get some advantage on the interest rate. Do you actually intend to rent then? A buffer is perfect in your situation anyway, you can sell ETFs if necessary. Of course, you can also work with short terms, etc. It’s all a question of complexity and desired risk.

Sensible approach and if you leave Germany out and really only invest in ETFs in the USA you will always beat the interest rate. There is simply a different stock culture there than here. The only thing you then have is the currency risk. Germans are generally more averse to debt and everything.

You don't need financial advice. Why should you? You know yourself well and in the end they just want to make money off you. I would negotiate the best interest rate with the equity you want to use and then go for it. You hold the trump cards and for the bank the deal is risk-free.