01-20-2011, 05:16 PM
It depends on the complexity. A simple handshake should suffice if you feel your relationship and personal knowledge is strong enough to trust the other person. If the services are more extensive (I'll build and maintain your internet presence if you'll build me a house), then of course a legal contract is in order (and don't forget to pay income taxes on the fair market value, alas )
I am not a tax attorney or CPA, nor do I play one on TV. Free advice is worth what you pay for it, YMMV, not liable for any personal, public, or galactic damage caused.