Hi,
I can only refer you to your current contact person at the bank – as a self-employed person, you should actually have this advisor. They may possibly involve a construction financing specialist from the bank.
You should bring all relevant data. That means, as a self-employed person, you probably prepare a BWA or balance sheet annually, from which the profit is visible. Even better, the profit after taxes. Based on the last BWAs, you can prove to the bank that although your income fluctuates, every year there was a total amount X overall. The bank will certainly make a safety deduction on that.
Then you should sit down and create an overview of your fixed monthly expenses. In addition, you should get an overview of how high your monthly living expenses are (groceries, clothing, shoes, online shopping, restaurants, cinema, going out, etc.).
It’s not possible to say flatly: you need the amount X in monthly income. None of us knows your lifestyle and expenses. @toxicomolotow put it nicely: There are people with low income who can still afford their monthly installments through an adjusted way of living. And there are people who blow >10,000 euros net income every month.
Regarding your idea of 2,000 (4,000) euros: Depending on the interest rate for full financing, it should work if the above data fits and the bank agrees.
2,000 euros p.m. = 24,000 euros p.a. --> that means with a 600,000 loan it is about 4% annuity. Consequently, with a 3% interest rate, a repayment of 1% is included. If you do not make special repayments, you will be finished after >40 years. Incidentally, I consider it sensible to aim for a fixed interest rate period of 15 years.
4,000 euros p.m. = 24,000 euros p.a. + 24,000 euros special repayment – The bank has no problem if you agree on 5% special repayment (= 30,000 p.a.).
The 16 - 20 years you are aiming for can only be achieved through consistent special repayments.
Why do you want to leave your equity completely out? (Security for self-employment as a buffer; planning incidental costs and for new furniture or similar)?
In general, everything depends on the assessment of your income and the level of your living expenses. Only your bank can tell you this – most sensibly the advisor who has been supporting you in self-employment for years.