600,000 how to finance? Income 600,000, combination with KFW?

Good evening,

due to the slope of our plot, we have decided to build a granny flat in the basement and rent it out, which is why we now need a loan of 600,000 euros.
More like 550,000, but I want some buffer.

We currently earn 6,000 net per month, plus the bonus/Christmas holiday pay.

Since I am currently abroad for work until 08.10, we can only see a financial advisor after that.
Nevertheless, I would like an assessment of whether we will get a loan and at what interest rates roughly and what options there are to improve the interest rate.

We keep a household budget and currently have about 2,500 euros left per month with rent of 1,550 euros. So basically, the installments are not a problem for us.

We are building KFW 55 and could take advantage of the KFW loan twice at 120,000 euros each, but they only have a fixed interest rate for 10 years.
How did you do it? Building savings contracts offer a bad interest rate, as do forward loans. What about repayment changes so that one mainly repays the KFW first? Of course, this only makes sense if the interest rates of the other loan are not significantly higher.

How do you assess our situation? Do you have any tips?
Equity capital is only about 80,000.

I think you mean the KFW 153 for KfW55 standard and KFW 124 for owner-occupied residential property. The latter only has a maximum loan amount of 100,000 euros.

We have a financing sum of around 500,000 and only took the KfW 153 because of the repayment grant.
We left the second one out. For us, the remaining debt and thus the interest rate risk after 10 years was too high.
But everyone has to decide that for themselves.

The interest rate is hard to say. It always depends on how long you want the fixed interest period, how old you are, how secure your jobs are, etc.

I estimate it to be around 1.1%.

No, he means 2 x 153 because of the [Einliegerwohnung]. My opinion: Looks good, but without our questionnaire, quite a lot of information is missing.

Income fits, savings amount fits, equity fits.

One could also discuss topics like children and parental leave, but I think that fits as well.

You have my blessing.

No, he means 2 x 153 because of the granny flat. My opinion: Looks good, but without our questionnaire a lot of info is missing.

Wow. I didn't even know that was possible. Then I would probably make use of the total €36,000 subsidy.

I will never understand why someone rents out an apartment in a "single-family house." Then I don't need a house if strangers live on the property. Payments are okay.