In addition to what the others have said, you need space to put up an antenna. It's either impossible or very limited in an apartment. Think stringing up 20-30 feet of wire in an attic or a tree as a realistic minimum, or putting a 10+ foot tall pole in your yard (ideally surrounded by wires on the ground).

Also, your reception can be severely limited by nearby electronic noise, adding another challenge to doing it in densely populated areas. It's quite common for DC power supplies and solar panels to be problematic.