How did people acquire housing in medieval cities? Were there analogues to modern-day real estate agents, or would you just have to ask around seeing if anyone had a room to rent, or a house/estate they wanted to sell? Or would you have to find unoccupied, unclaimed land and build your house yourself?
I know that people moved around a lot less and the concept of buying or selling a house would not be a common one, but certainly there was a demand for new housing of some kind.
Obligatory "medieval Europe can mean a lot of different times and a lot of different places." You should probably make your question a little more specific.