Check profits
If you are considering buying a business, you need to check up on whether they make the profits they claim to make.
The prospective buyer can probably ask for a profit loss statement, but it is always possible that it will be "embelished" . So the buyer should do his or her due diligence before taking any kind of decision.
You can get started by asking the local librarian how to research profits for the type of business you are interested in buying. Your librarian should be able to come up with some statistical data and/or the addresses of any applicable trade associations.
Then contact the trade associations ask what them to identify the major problems facing the industry.