Costs & Funding Assessment

The first step would be to go to your house bank so that you can at least get a rough idea of where the bank sees your limit. But please under realistic conditions. So don’t let yourself be talked into a 10-year fixed interest rate or 1% repayment just to make the installment fit.

Your wish is for about a 30-year fixed interest rate, so stick to it. With 30 years as a full repayment borrower, you would come to a rate of €590 with €150k and an interest rate of 2.3% (assuming 80% loan-to-value - but this is pure speculation and the bank will calculate it for you); plus additional costs, you would/would have to spend somewhere around €900-1000 monthly costs for housing.

I hardly believe that a primary bank would provide 150k mainly for own contribution to construction/renovation.

That is one size too big

The first step would be to go to your house bank so that you can at least get an indication of where the bank sees your limit. But please under realistic conditions. So don't let yourself be talked into a 10-year fixed interest rate or 1% repayment just to make the rate fit.

Your wish is for around 30 years fixed interest rate, then stick to it. With 30 years as full repayment, you would come to a rate of €590 with €150k and an interest rate of 2.3% (assuming 80% loan-to-value – pure speculation but the bank will calculate it for you), plus incidental costs you would/would have to bear monthly housing expenses somewhere between €900-1000.

Well estimated :O I currently have an offer for €150k at 2.18% with a fixed interest rate of 29 years and 4 months. The rate would be €542 with a remaining debt under €20k, so with €590 there would be no remaining debt at the end.

The loan-to-value ratio is 76%

I consider 30 years to be an insanely long time, especially at such a low rate. You are (still) alone, there is still so much that will happen. Overall, I don't think the whole thing is the best idea ... but there may be other life plans ...

My suggestion would be that you first make a list of everything that needs to be done. Possibly with the help of a planner. Then break down what you can do yourself and how much it will cost. Save the planned loan installment. Things like replacing windows you can already start tackling gradually. Can you build the extension on your own? I would first try to do as much as possible without a loan. Whether you will get by with 150,000 is certainly a question of the equipment and how much you can do yourself. How much time do you plan for the renovation? Do you want to stay living there during that time or will there be additional expenses for rent? We have been renovating our old house for 4 years now, without a loan. The extension was completely done ourselves, windows, floors, outdoor facilities, carport, etc. – it’s possible, but there is a lot of work behind it. And living on a construction site at times, although we have the advantage of having over 200 sqm available and can move out more easily.