Actually, I know 2 people that “flip” houses and have been doing it for years. It takes capital. You have to be able to make an offer or buy a property as soon as it comes on the market. Typically here in NH that means you have $300K to $500K cash on hand or a bank credit line for at least that. This is not Detroit or Cleveland where you can buy houses for under $50K.
The other thing that both of these contractors have in common is they get their hands dirty. They do not hire other contractors to do all the work like you see so often on TV. My one friend has a bulldozer, backhoe and an excavator. He also has a full woodworking shop to do any millwork projects himself. These guys drive pick up trucks not Porsches.
This TV show and money-making scheme is not about doing it the right way. Of course, skilled businessmen with capital can make money. This advertisement is aimed at dummies with no capital.
Doing your own work would be more tax efficient. Your labor provides value in a way which is taxed as a capital gain and not income.
When I was a graduate student at Purdue, back in 1955, one of my friends came from a family that did just that, in the St. Louis area. Buy a run-down house, put it in shape, and sell it. Apparently her family made a good living at it, but it took work. I don't think the term "flipping" had been invented yet, and what they were doing wasn't really "flipping" as it exists today. "Rehabbing" comes closer. They were adding (or restoring) value, not just waiting for the bubble to grow bigger.