This is the part of the loan that the person who lends money to you does not think you have coverage for in the form of collateral called a top loan. Therefore, this part of the mortgage loan can be taken out in the form of a loan without collateral.
The most common is that the top loan falls somewhere between 5-15% of the total loan amount. This is so when you normally have the house as collateral for up to 85% of the loan (the bottom loan) and after that there is a cash deposit of about 10%. Remaining will then be about 5-15% which you can take as a top loan. This assumes that you do not have the cash and can pay it yourself.
Since the top loan is a unsecured loan, this means a greater risk for the lender. Should you not be able to repay your loan, they can take the house as payment for the mortgage, but they cannot do that for the top loan. Unfortunately, as a borrower, you will have to pay a higher interest rate for your top loan. However, these are not very high interest rates for this type of loan, only that they usually lie a bit above the mortgage rate.
This means that you want as little as possible in the form of top loans and that it is precisely the top loan that you try to repay as quickly as possible since that is what costs the most money to have.
The most common is that you have a so-called variable interest rate on the top loan and that the repayment period for the loan is somewhere between 10-20 years.