When you say wage are you speaking an hourly wage or a salary? Can I assume you'll be working with a mystery shopping company and not a scheduling company? It sounds to me like you're referring to being an employee rather than an independent scheduler who generally work from home.
A mystery shopping company is likely to pay you a wage in you're working in hourse. You will have clients or territories assigned to you. You'll certainly be expected to fill shops but you won't be paid per shop. You should have a certain amount of shops you're going to be expected to get filled and submitted within a shopping period. The number of shops may fluxuate depending on a variety of situations - some clients have very odd shopping schedules so the number of shops can vary widely during different times. If, for instance, you are scheduling monthly shops. you'll be expecteded to get all of them scheduled and submitted. If something's wrong with any of them and they are rejected in editing, you'll have to fill the shop and get it submitted again. You won't be paid more because you filled 2 shops.
Also, let's say in the month of October, because of different shopping schedules, you have 1000 shops to fill but come along in November, you have 1500 shops to fill. You'll likely be paid exactly the same for both months.