That is a pretty generic question, since many other factors go into the price of a home as far as location, and condition, which are much more important than if a home has a garage or not. If I had to absolutely put a price on how much more a home with a 1 car or 2 car would be, I would say that in any given area a 1 car adds about 10% value to the homes that have no garage and a 2 car would add about 20%.
For example lets say in a neighborhood that has a 1,400 sq ft home built in 2000 with no garage sells for $100,000, then I would estimate the same home with a 1 car garage at $110,000 and a 2 car garage at $120,000. But since you won't find 2 homes that are exactly alike it is hard to give a better idea of how much value they add.
I hope this information helps, but keep in mind this is my opinion and just an estimate.