You should basically always be very suspicious when someone is trying to sell you a way to earn very attractive returns without a lot of risk or without time and effort intensive management. There is a lot of capital out there in the world looking for a return. If the returns really were so attractive on a risk-adjusted basis, and you could deploy a fair amount of capital without building a large organization and incurring a bunch of fixed operating expenses, why wouldn't someone who is a proven successful operator in that field just raise more capital themselves and keep more of the profits?
Even when the propositions look plausible on the surface, there is usually some hidden gotcha that prevents it from being scalable. For example, the economics only work if you can find a really good location that meets a bunch of requirements, and there simply aren't that many of those "good" locations left. Or it turns out that it requires very intensive management to deal with broken equipment, theft, vandalism, etc.
Even when the propositions look plausible on the surface, there is usually some hidden gotcha that prevents it from being scalable. For example, the economics only work if you can find a really good location that meets a bunch of requirements, and there simply aren't that many of those "good" locations left. Or it turns out that it requires very intensive management to deal with broken equipment, theft, vandalism, etc.