Is it standard in the US that dive shops contract that you must buy your gear from them?
If it isn't in any small print, then I can't see how a LDS can object that you made a consumer decision to purchase elsewhere?.....providing the gear is safe and suitable.
There is no contract and no real requirement to buy any gear from anyone. But there are expectations of the LDS and there is attitude!
"How come you bought your stuff over there?"
"Don't you know you should buy locally instead of on the Internet? How are you going to get air fills if we go out of business?"
"That <brand name? stuff isn't anywhere near as good as what we sell for less."
"You better bring that (brand new) gear in so we can do a safety inspection before class."
"You won't get a warranty with that stuff you bought on the Internet and it's all grey market stuff. Who knows what inside that regulator. Probably reject parts bought as trash and then assembled (and put in factory boxes)."
And on it goes...
There was a very long thread here a few months back about a student being tossed out of a Nitrox class for buying their computer elsewhere. I hope I am recalling this correctly.
It's not that the questions above are hard to answer and a diver may have very good reasons for buying the gear elsewhere, including via the Internet. It is the conversation that is ugly. I'm not the kind of person that takes much crap. I'm basically not in the crap taking business.
What Thalassamania was saying is that if you find a truly independent instructor, they won't care where you bought your stuff. They aren't in the business of selling stuff anyway. They're instructors. They will expect quality gear but they won't care if it is ScubaPro, AquaLung, Oceanic or whatever as long as it is in good condition.
What I said earlier was that, having already decided on an LDS and having made a commitment to them for training, it is best to avoid the ugly conversation that WILL ensue if the OP shows up with gear from another source. It's better having made this commitment to just delay the high dollar purchases until after the training and avoid the crap. Besides, after the training, the shop knows you can buy anything from anybody. Your involvement with them can come to an immediate end. Pricing may improve when they know you can shop anywhere without their pre-training wrath.
That's why you want to use a disposable LDS for your OW training (if you are not using an independent instructor). You buy the absolute minimum gear from them, take the OW course and walk away. You then buy your gear wherever you want, deal with the service issue in whatever way works for you and when you go for more advanced training you use a different LDS. They will see you walk in already certified and it is expected you have the bulk of your equipment. A simple plan for avoiding conflict.
Richard