I got a rat job. 2 acre pond and a creek. I'm also gona catch the one beaver there. How much do you guys charge for rats. PM me if you like. I prefer the per animal method with a set up fee.
I already set it up. I done beavers for this industrial park before. And he said "just make them disappear".

I charge a weekly rate for that type of work.

Estimate the time it will take to set up on the 2 acre pond. Then the time it will take you to check the pond each day x the number of checks you think it will take. That is the total hours of the job. Multiply that times the rate you want to make per hour.
Next figure out mileage to and from the job x the number of days. ($.555 per mile is what the IRS is at for mileage)
Insurance, auto, liability, any other expenses such as four wheeler gas, trap loss (especially at golf courses or public parks)
Last, what will you make on the pelts? Some figure this as pure profit.
That is your total job cost. If you want a per animal rate, divide by the number of animals you think you will catch.

I find it easier to give the customer a flat rate for a trapping job. They know what it is going to cost in total and I know I can cover my costs.
Good luck and whatever you do, just keep track of your time and expenses so next time you have an opportunity, you know how you fared on the first one!