Sorry, but sadly we can't. There are too many variables. If you become a mystery shopper, you are essentially becoming a small business owner and will need to create your own opportunities. The forum is a valuable resource because it will take research and time spent registering with as many mystery shopping companies as you can. Beyond that income will vary depending on your market and how saturated it might be, your skill set and how much you are willing to invest in your business in both time and money. Most mystery shoppers who actually make a living at this also do a lot of traveling. Successful route building is a skill that takes time to learn and is enhanced by solid experience and building up a good reputation with mystery shopping companies. Depending on your goals, it will take more than 40 hours a week, especially in the beginning. Available jobs also fluctuate so while you may eventually be averaging 40 hours a week it may come in the form of several 80 hour weeks followed by a week with nothing.
Spend some time here reading and researching and you will understand what I mean. A lot of people have been, and continue to be, very forthcoming with tips and advice.
Equal rights for others does not mean fewer rights for you. It's not pie.
"I prefer someone who burns the flag and then wraps themselves up in the Constitution over someone who burns the Constitution and then wraps themselves up in the flag." -Molly Ivins
Never try to teach a pig to sing. It's a waste of your time and it really annoys the pig.