I give em 24hrs max. I always prefer paypal, but if tthey have enough positive feedback and request to pay money order i usually let them. Although I don't ship the item until the money order clears.
If they have no feedback I usually make them contact me before bidding//buying it now just to make sure they are legit, and are not scammers
It usually works out well, but I have had a few incidents w/ scammerse in the past, and it is time consuming especially when the click buy it now, and then send you an e-mail stating they want the item shipped out of the country blah blah blah.