I don't know where you are located, but in NJ, a substitute teacher makes about $20 per hour and some school districts pay more. Maplewood, NJ for instance just raised the pay to $175 per day. If you worked every one of the 180 school days, that would amount to $31,500 per year (actually, 9 months). While some on this Forum have said that they make that much, they are in the minority, and they often have to plan multi-day routes to accomplish that. As a mystery shopper, you also have to factor in mileage (I usually assume that 1/3 of my gross pay will be deductible at the IRS mileage rate). I doubt that you can replace substitute teaching with mystery shopping on a consistent basis. Others on this Forum may offer different advice.
Shopping Southeast Pennsylvania, Delaware above the canal, and South Jersey since 2008