There are two issues, one is payment (and using Paypal mostly solves that issue) but the other issue, which is just as important to me, is whether the individual can be depended on to deal with you reasonably.
People with positive feedback at least have a track record of working well with others. If the feedback includes both buying and selling, and transactions for at least a few higher priced items, to me that is even better.
You already received some good advice from rockadanny and I would add that, for me, the desire to deal with somebody who has no feedback would also depend on the value of the item I was selling. I am inclined not to sell big-ticket items to folks with little or no feedback and I state that in my ads. Selling a pair of $200-300 cables is one thing but selling a $5-10K amplifier is something else entirely.
I should add that I won't purchase from sellers who have no feedback because of the same types of concerns.
My advice to those without feedback would be to start by buying a few lower priced items simply for the purpose of establishing feedback here.