In standard Mandarin,
屋 is not commonly used as a noun by itself. Though,
房屋 is a common word, which is very similar to
real estate in English. e.g.
Real estate agency.
Another common usage of
屋 is in forming a name of a special kind of house. In such usage, it normally has a quite cozy feeling, e.g.
小屋 is a hut,
淑女屋 is a female clothing brand name.
I get feeling that the use of
屋 was may be introduced from Japan in modern times. Just a wild guess because
屋 seems much more common in Japanese.
It is quite widely used, and is very similar to the English word "house".
I have a house.
Old house, etc.
屋 is not as widely used in Mandarin as
屋 is used in a more formal fashion compared with