It's how mortgages work. You make a monthly payment to live somewhere, same as renting. In the rental scenario, it all stays with the landlord. In the mortgage scenario, you have paid off some portion of the price of the house. When you move out, you sell the house, and use that money to pay the rest of what you owe, and the difference is yours. It's like selling your car when buying a new one, except housing in the US tends to go up in price even when used.