I just did the math for a small route around my home with 6 in my home town up to 5 miles away. 29 shops total. It would have to be done in 2 days because I can only complete 20 a day. It came out to 6.69 an hour after I factored in drive time, onsite time (10 minutes), report time (15 minutes), unreimbursed purchase @ 25 cents (rare find!! more realistic is tea or chips @ 99 cents), and gas. BUT they also have to be reported in 12 hours or your fee is reduced. So actually this would probably make it a 3 day route. I had myself driving 7 hours on day 1 of the route, this didn't include on-sight time. There is no way I would be able to turn the early day shops around in 12 hours.
I would consider these for $15 plus reimbursement up to $1. Honestly, I have done these, I know what they take, I understand the audit (same as before). The audit itself is very easy, but it all takes time. I'm not out to get rich, but the fee being offered isn't fair. Your time is worth more than less than the minimum wage offered....even for the experience.
Sit and do the math. Look at a route. MapQuest it. Factor in 25 minutes for on-sight and online reports. Factor in gas, and unreimbursed purchases. Then factor in your drive time.
I'm not jerking your chain, just being honest. $15 plus reimbursement is an honest price.