First you should consider whether you really want to have clients come to do a photo shoot in your garage. Personally, I wouldn't want to use my garage or do a shoot in someone else's unless the garage itself were an important element of the shoot.
You have at your disposal the most beautiful light and backgrounds for free. Shoot outdoors. No lighting to buy or set up or transport. You get that perfect natural light. All you need to harness it and mold it for your work are a few diffusers and reflectors. Used properly this is the best light you can expect to have. And the natural scenery is so much nicer than fake backgrounds. Although I do understand that a nice solid background can be great too. Nothing says you can't use a medium sized background outdoors.
edit-Okay, no offense intended. Very few garages are nice inside. Personally, I just don't want a studio in my home, not that I have room for one in any case.
I have never used a lighting set-up, just flash for artificial lighting. I do know that you will need some sort of background and a support for it. The staples for backgrounds are black, white, either brown or gray, and blue. You could look for double sided backgrounds if you can accomodate that kind of set-up. Paper backgrounds are the cheapest but they get damaged easily and don't look at nice as muslin. You can buy fabric and make your own, but it may be easier for you to just buy the backgrounds.
I also know that anything you need you can buy at B&H. They sell lighting and background kits and have fair pricing.
