See a few gas station audits on the board listed for $18 each. How long do these audits take to complete and input? If it's only like a 15 minute audit with mostly yes or no questions, and a few pictures then maybe. Otherwise I might pass on it.
It also depends upon how large the GS is and what types of fuel they sell. The little gas stations with 3 or 4 pumps are pretty quick. When you get those mega stations with multiple fuel types it takes much longer and may not be worth your time.
Where I live the shops are $9, plus $5 reimbursement for gas. You have to buy 2 gallons of gas and spend $2 on any food item. I did a few of them, but stopped. They're not worth the time.