So in 6 years we can additionally afford about €1300 per month through a large photovoltaic system
???
Why can you afford an extra €1300 per month there? Is the system supposed to generate that much monthly profit in 6 years? Who calculated that for you? Is the system already installed?
Generally, people say max 30% of net income? The bank advisor said it's okay......
If only it were that simple...
Is that YOUR net income? Or is it yours and your girlfriend's combined? What happens if one of you becomes unemployed? Do you want children? Can you manage everything with just one income then? Have you ever thought about the case of separation?
But even if everything goes smoothly: what exactly is included in those 30%? Meaning, how high is the repayment portion? You can pay €1000 per month on a €240,000 loan but also €1500 or €2000... The one who only repays €1000 will still be paying off his house in retirement, the other will be debt-free after 15 years...
To make the numbers look better, people often only calculate with 1% repayment... in my opinion, one should not start below 2%...