Not all Rescue Groups are in it for the money, but I do have to say that I know of two that are. One is very popular, has been in trouble in the past, and if you see the price of adoptions, you know why. The other just takes dogs in, doesn't spend money on their medical needs, and then just adopts out.
I wouldn't put all rescue groups down by a long shot though, but just do your homework before adopting from rescue as well.
The dogs that need a home the most are those in shelters. Shelters do take care of the animals medical needs, but most are kill shelters that don't hold them very long. So sad.