Business ideas are difficult, if you overthink it you might not even try it, you will get analysis paralysis.

Business that are already running are the best benchmark. Literally, if you launch an existing business with a little twist you could end with a better business than innovating and starting from scratch.
If the business has some time running the path, market and niche are verified and tested. It is profitable.
Cashflow and investment amounts may vary, just need lock in a business that is reachable, a business that you have the money to start and you are willing to commit. Long term.