PigMoney…..
Is any special license needed to sell them?
No, you do not need a license to trap (with landowner permission, although I always have my hunting license) nor do you need any kind of license to sell them to an approved buying station. It is illegal to transport them anywhere other than directly to an approve buying station with the exception being you can sell boars and only boars to high fenced hunting operations. I've never done the later so not sure about the exact requirements on that.
To me, it is a hobby that pays for itself in time.