Interesting question. Do you know what kind of "vape" they are selling? Texas has some interesting laws around CBD. If it is hemp derived and below the .3% THC threshold then it is legal. CBD with a higher THC content, up to .5%, is legal with a medical card. If their vapes are CBD related, then you'll want to do due diligence around them, and monitor to make sure it's not a front for illicit activity. But, because hemp is legal, no additional filing requirements are in place.
If on the other hand, the vapes are not CBD related, and say just run of the mill, fruit flavored stuff, then you'd treat them the same as if you had a store that sold beer or cigarettes (which has a minimum age requirement).