increasing detached garage size for additional rent?

[Jake T Gilts]

Interested in to see what your opinions are on an idea of mine. I have a sfh home with a detached garage at the rear of the property, the property is a corner lot with an alley behind the garage so there is access from both sides of garage. My question is currently it is a 1 1/2 car garage and I had the idea of rebuilding it and making it a full 3 or 4 car garage and renting each space for 100 per unit which would add 300 to 400 to my current rent of the house which is renting for 750. The property is paid for just looking for a way to expand, or should I just save my money and use it for next investment?