Buy house/property, financing possible? Interest rates?

Regarding your points 4 and 5:

As I already wrote: It’s best to go through a financial broker. I recently had good experiences with Hüttig & Rompf; neither my house bank nor other financial brokers could match their conditions. In 2008, however, it was Interhyp that got me the best conditions. So: try it out and inquire, it only costs time. And since every broker/bank requires roughly the same documents, you will have to put them together anyway.

Interest rates depend both on creditworthiness and the loan-to-value ratio of the property, so it’s hard to say anything reliable here. It makes a huge difference for the bank whether they are supposed to give you €200,000 as a construction loan when, according to their valuation, the house is worth €150,000 or €200,000 (keyword "loan-to-value ratio"). Therefore, it is generally difficult to generalize.
Of course: the longer the fixed interest period, the higher the interest rate. If you want 15 years or more, there will probably currently be a 2 in front of the decimal point; the decimal places then depend on your creditworthiness and the property. And yes, for most customers I currently recommend the longest possible fixed interest periods to lock in the low interest rate level. If you also secure both a right to make special repayments and a multiple free right to change the repayment rate (you can then increase or decrease the rate during the term and thus influence the length of the loan), you are pretty much on the safe side. Furthermore, everyone has a special termination right according to §489 Baugesetzbuch if they have concluded a fixed interest period of more than 10 years. With this right, you can terminate the loan at any time after the first ten years with six months’ notice, no matter how long the fixed interest period still lasts. So if we all meet again in 10 years at such favorable conditions, you can always pull out §489 Baugesetzbuch and secure a cheap follow-up loan; thus, long fixed interest periods tie you up at most 10 years and 6 months (after full disbursement). The bank, on the other hand, cannot exercise this right and is bound to the contractually agreed fixed interest period.

Hüttig & Rompf and I also recommend great support and good conditions.

Sure: The longer the fixed interest period, the higher the interest rate. If you want 15 years or more, there will probably currently be a 2 before the decimal point, the decimal places then depend on your creditworthiness and the property. And yes, for the vast majority of customers I currently recommend the longest possible fixed interest periods to take advantage of the low interest rate level. If you then also secure both a special repayment right and a multiple free right to change the repayment rate (with which you can increase or decrease the rate during the term and thus influence the term), you are pretty much on the safe side.

I find that somewhat generalized. You should definitely calculate how the interest rate might develop after a fixed interest period, whether you are better off with a longer fixed interest period. For example, I am glad that I signed for only 15 years instead of 20 years. The additional interest rate was quite high and if I can continue to make our previous special repayments for another year or two, after 15 years I will have a remaining debt somewhere between 0 and 50,000€. If one had known beforehand that everything would go so smoothly so far and the interest rate would not rise exorbitantly in the next 7 years, probably even a 10-year fixed interest period would have been worthwhile.

Also, the double protection through repayment rate changes and special repayments is probably costing a few tenths of a percent.

Thank you for the recommendation with Hüttig & Rompf. I have never heard of them before. So, I currently also favor 15 years. Of course, there will still be a residual debt of about 50k-70k, but I also have my Riester contract, which I want to convert into a Wohnriester after the term. I took this out 6 years ago and also pay the full amount into it. And I plan to continue doing that in the coming years, provided no financial difficulties arise for us. After 20 years and full contribution rate, a good amount will have accumulated.

Interest rates depend both on creditworthiness and the loan-to-value ratio of the property, so one can seriously say little here. It makes a huge difference for the bank whether they are to give you €200,000 as construction financing, if according to their valuation the corresponding house is worth €150,000 or €200,000 (keyword "loan-to-value ratio")

So, if I buy a property, does the bank ALWAYS send me an advisor who determines the value of the house?

So when I buy a property, does the bank ALWAYS send an advisor to determine the value of the house?

It works like this: The bank gives you a checklist of documents they would like to have regarding the property (land register, building documents, cadastral map, ...). Afterwards, the bank evaluates the property based on these documents + their internal systems (the bank has respective databases where comparative values for the respective street are stored). In addition, either someone from the bank or a service provider comes out and takes at least exterior photos, often also interior photos. With all this information together, the bank then calculates the internal lending value, which is important for the feasibility of the financing and the interest rate.

For more information about the lending value, enter this term in Wikipedia (links are not allowed here in the forum).