from what i know of low bid sites...you must have the lowest unique bid to win the item, but you have to buy something like "bid tokens" to bid. so the cost of the bid token plus whatever the bid you bid if you win. you can bid as many times as you want as long as you buy enough bids to use.
thats about it, you can't bid with out a bid token, though usually the first bid is free when you sign up.