If you're door and window aren't ever open and the sun doesn't shine on the cages directly from the door or window and you don't live in a cool climate where cool/cold air could hit the cages then it should be fine to have the cages there. If you place the cages in a row you will need a visual barrier between the cages. If the cages are placed so that a chameleon in one cage would be able to see another one (for instance, across the room), then it could be a problem too.
You asked when you have babies..."do you need to separate them? Or can they all go in the same cage?"...whether or not they can be kept together as babies depends on the species and a few other things. If its a species that can tolerate or even "needs" other babies with it, then I would recommend not keeping very many per cage. They usually need some space. You need to watch them too...and if one is not growing as fast as its siblings or not getting its share of the food, then it needs to be separated out. I keep veileds in groups of about 5 per 10 gallon aquarium....but panthers and C. chameleons I keep individually usually. Here's a set-up that works for ones that you can keep in small groups...its a plant stand which will hold several cages per layer...has two places for florescent fixtures and two places for incandescent lights (if you need them).
http://www.chameleonnews.com/year2002/nov2002/horgan/1pic.html
You said..."My idea is to sell a few as babies, and then raise them to be a couple months old and sell the rest. Is that they best way?"...to be fair to buyers, I never sell my chameleon babies until they are about three months old. There is a natural mortality rate...not all will survive as a rule....and I hate to sell one to someone and have them tell me it died shortly after they got it. Just my opinion...