If you are not a World Ranked top 20 pro player, it is very hard to make enough to live off from playing TT.
In New York, I know many more TT clubs that have closed because they could not bring in enough money to keep the doors open than I know of ones that have been successful and stayed open for years. And it would take a decent amount of cash up front to open a facility. Worth knowing it would hard to ever make enough to break even and just get your initial investment back.
Selling TT equipment....does that sound like it would be fun? You could sell anything if you like the idea of being a salesman and I would put money on it you could make more than you could selling TT equipment since TT is such an niche sport with a small but dedicated group of players who really follow, in comparison to other sports.
But yeah, if you were someone like Tony who is a A+ coach and is known and has a reputation, you can make it so you do a little better than just barely getting by.
But the idea of Med School vs trying to make enough money off a Table Tennis hobby/addiction.....well,
If you don't have a problem living on bread and water go for it. Otherwise go to the golf range.
That kind of sums it up well enough. As long as you understand, sometimes that would be bread one day a week and sometimes water. I even know guys who are 2500 level players, decent level coaches but have a day job because the work coaching TT is not reliable enough.
It is a great sport to play and be involved in. But I can't think of anything that it would be as hard to pay your bills with. And being someone who turned a few hobbies into things that paid the bills, TT would be last on my list for that.