There are many directions you can take this business. If you want to work during hours when no one else does, you can focus on office clients. You can focus on retail businesses and keep your customers clumped into one or two blocks. Restaurants are in great need of daily thorough cleaning and can be a great source of steady clients. Perhaps you would be more interested in house cleaning. Many times with cleaning services you don't have to spend lots of money on advertising or marketing because your customers will come by word of mouth.
What’s the catch? None, really. Cash back apps act as affiliates for many online merchants, which means that whenever you make a purchase through one of the apps, they get a small commission — but then, they give you a portion of that commission as “cash back”. For example, if I buy a pair of Nike shoes through the Ebates app (or website) and spend $75, Ebates may get a $10 commission but then they’ll pass $7 back to me. It’s basically a way to get sale prices on stuff that isn’t on sale!