Same as making income from any other business.
Find out what people want by trial and error. TRIAL AND ERROR.
Don’t listen to anyone except your customers.
If what a customer says doesn’t match where they spend their money, ignore what they say.
Don’t get hurt.
Don’t hurt anyone.
Do a job other people don’t want to do. (Everyone wants to petsit kittens.)
Cesar Milan, dog training guru, works with dogs so dangerous that NO ONE ELSE will even try.
End of part 1.