Back in the 80's I owned a "Off road extrication service" I had set rates, proper licenses, proper insurance, damage waivers to be signed by the vehicle owner, plenty of properly rated equipment and training/experience to use it.
I had a vehicle and equipment able to get into places that normal wreckers could not and would not go.
Overall it was a money loosing deal. No matter how you rig for a winch pull damage is a possibility. Even after explaining this to the owner, having the waiver signed and immediately prior to the damage happening warning the owner that it would likely happen and getting verbal permission to continue, you are still subject to be sued and just as noted above, once in court your lawyer may well be able to have you relieved of financial responsibility for the damage, but lawyers are not free and neither is your time.
People rarely carry enough cash with them while out playing in the mud/woods/desert so you have to accept a check or payment after the fact. Often you will never get paid. If you insist on payment up front and then are not able to effect the recovery, they want a full refund. No matter how badly they got themselves stuck, no matter how far you had to go just to get to them, no matter what time of day/night/holiday/wife's birthday, no matter how long you worked on trying to help them and no matter how much or your expensive equipment you broke in the effort.
I finally gave it up. Would I even think about doing it w/o the proper licenses, insurance and truck plates? No way. It is really nice to be able to help people but these days it is just not worth it. If it is a known friend that I know will/has helped me, no problem. My friends know not to give out my number. If it is a family member of a friend, I'll probably go. A friend of a friend of a friend... I'm really sorry but I just can not accept the liability anymore. Not to mention it gets the truck all dirty and you know the "Stuckee" is not going to come over and wash the truck for you, much less pay got a broken winch cable, or whatever.
A SS member that posts he is stuck and asking for help? (And is not 4 or 6 states away like the last two...) Sure. That is different. You guys are family...
(Bet you still don't come wash my truck though...lol)
If you are going to do it, I would highly recommend you become exceedingly familiar with numerous different techniques of extrication and review the equipment list I posted previously and then get 50% more stuff than that. Read the instructional TM that was posted in that same thread, (A couple pages before my post). Read it several times and then go practice all the techniques in the manual. If you start charging, you become a "Professional" and in court you will be held to a higher standard than you would as a simple "Good Samaritan " And don't forget licenses, (City, county and sometimes state) insurance, properly licensed vehicle, some places even require certain training certifications and truck/equipment inspections/certification....
http://www.steelsoldiers.com/deuce/62241-help-need-pulled-out-mud-houston-pasadena-tx-7.html
Hope this helps some...