Mystery Shop Career Path

Last fall I decided I wanted to make a little extra money and signed up with several companies to do mystery shopping. I wasn't sure that it would be something I liked as I wondered why I would go out to find hassles in my life when they come to you unsolicited (I mean things like bad service, poor attitude, etc.)
The first adventure was a dinner that needed to be done at a certain time to make sure the crew wasn't closing up too early. The food was bad; staff was dis-interested. The time required to do the report, have it critiqued, revise it and wait for payment would have been ok if the food had been decent. So, is a $23.21 free dinner worth it? No.
Then we did a few snack type ones, which were fun, but took more time to get there than it was worth it for a free coffee.
My final experience was one where I think I was misled. It was for valet parking and reimbursement was for the parking fee, a tip, a shop fee and, from the instructions, a snack while waiting to pick up the car from the valet. I re-read the instructions many times to make sure I got it right. But, in the end, the snack wasn't covered and the adventure COST me $12.00 more than I netted from the shop fee. Lesson learned. Done. Not the career for me.
As my husband just said when I told him this story: "Next time, make a career choice where you don't end up in the negatives." Point well taken.