IMO, it should be 16. It should be the earliest age that you can work in a traditional job, or begin service in one’s armed forces. Many right-wing people hate this idea because young people are very left-leaning, but it is unfair to expect someone to contribute to a society that bans them from having a say in its outcome.
I knew a guy that was really into his hookers from sex worker sites and the prices he’d say were shockingly cheap. He got regularly checked out, and after years of doing this (at least 5) the guy says the only STD he’s ever got was chlamydia, which was in his “pre-hooker days”.
That’s all to say that you’re probably fine, but you should definitely get tested for peace of mind. If they’re sex workers by trade, they’re probably on top of the testing themselves.