Yes you do make the money by selling the cards. First you buy only the cards and players you want. Your cards will be in your online portfolio. The cards are kept in the topps vault until you request them for delivery. You can sell the cards through the etopps trading floor(which is hosted by ebay). Or trade the cards for other players that you want.
Did you check the buy and sell Forums yet? Looks like a "rousing success". Just one step below Yahoo on the scale of worthlessness. It's nothing but a pathetic attempt to emulate Ebay. Lotsa luck to them. They'll need it!