This sounds like a great job for you Sara and as others have said there's nothing wrong with getting paid for a job, professional or not.
Since you are going to be doing a great deal of driving I'd make sure I figured the gas into the price/hr and add a couple of dollars. Personally I don't think it's unreasonable as the price of gas here just went up to $2.65/gl

Good luck and I'm sure you'll do great!