There are a lot of AC systems repaired at stations that don't even own a recovery machine. (This is legal, so long as the system has already leaked out to nothing before starting the repair. I suspect that gets a wink and a nod a fair amount of the time.)
Some refrigerants can only be legally sold to resellers or to users with an EPA certification. Sounds strict, huh? Well...the 609 certification test can be done online, is open book, and cost me $25 and 15 minutes to get.