A mortgage is a loan you take out for buying a house. How much you can borrow depends on your income, the price of the house you want to buy and all other financial obligations you have.
To find out exactly how much you can borrow you need to arrange a meeting with a mortgage lender. That may be a bank, but you can also talk to a mortgage consultant if you prefer. Mortgage consultants can compare various types of mortgage and help you in making the right choice. Bear in mind, though, that taking out a large loan will commit you to high monthly costs for many years.

If you know how much money you can spend, you also know how far you can go during negotiations. Also bear in mind that 10% in costs is usually added to the purchase price. These are the 'purchasing costs payable by the purchaser': costs which the buyer must pay to have the house transferred in name to a new owner (transfer tax). This can only be done by a civil-law notary, who obviously needs to be paid.