what's the difference between "house" and "housing"?
I am confused by these two words and I am wondering what's the difference between "commercial house " and "commercial housing".

Question

Answer

"Commercial house" would be talking about the building itself, but "commercial housing" refers to the complex of houses or apartments as a group.

Answer

While Lee's answer above is quite correct, I thought that I should add that there are a few more meanings to the word "house" in a commercial sense. 
a. A commercial firm: a brokerage house.
b. A publishing company: a house that specializes in cookbooks.
c. A gambling casino. The house always wins.
d. Slang A house of prostitution. "cathouse".
An example:
The fair, which took place from Nov 20-24, included the participation of about 18 commercial houses. (http://www.thefreelibrary.com/Car+sales+grow.-a0353380072)