Check with your local high school/trade school/college as to their car repair classes. They will do the work for free or only a very minimal charge, for the experience. You will probably have to buy the parts.
Besides MCW's suggested link call around to all of your local auto repair places and ask what they would charge for a seeping compressor with a bad hose by phone. That should give you a better idea of what the fair going rate is in your area without an additional inspection charge.
This might sound mean, and it's sincerely not meant to be, but when I was an infant/child there was no air conditioning in our cars and I survived just fine even in stop and go traffic when the temps were even 90 and 100 so if you can't afford the repair simply use common sense when it comes to your children's heat safety.
Check out the following website for estimates.
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