OP, I've tried hiring via an app before and it led to a great experience. Make sure you confirm boundaries with the masseur before and afterwards, regardless of the type of massage you have with them.
If you plan on having appointments with them regularly, I would suggest switching to text/phone calls as your primary method of interacting with them - it may even make sense to block them on the app afterwards so you aren't breaching the line between professional and personal - you might even block each other if the experience doesn't go well.
Good luck! Hope this helps!