IRS Publication 535 may be of some help.
It gets a little tricky because there is a difference between having a business (ie. self employed) and having a hobby. Any good CPA/Tax advisor should be able to complete your tax return when required.
The most important thing is to keep meticulous records. Get a small book and for each day write down your mileage and all expenses.
I doubt that the mileage from home to your workamping site will be deductible but that's just my opinion. How to differentiate between miles to the site for leisure and for business?
My only expertise is doing income taxes for AARP each year for the past 10 at least BUT we don't usually get involved with such expenses.
Dick_B
2003 SunnyBrook 27FKS
2011 3/4 T Chevrolet Suburban
Equal-i-zer Hitch
One wife, two electric bikes (both Currie Tech Path+ models)