buy something not too expensive and test, for some of those places it is the only test possible. site can be just a side business, who knows.
if they take paypal/cards - use it, if only venmo etc - run.
Some people are still stuck in the 80s/90s when it comes to websites. Or don't have one at all. Sure, there's lots of argument to be made about how easy it is these days, but some folks just can't be bothered.
Like Paul said, give it a go on something small, see how they perform.
Ive caught a couple web sites that listed a legitimate FFL #, address, but wouldnt take credit cards for payment. Just that venmo and other shit payment methods. Be CAREFUL. They fake a website using real credentials.......