200 Bet Basket +EV?

[pokerrookie]

Complete newbie to sports betting...But Bet365 has the 200 bet basket. If I place a qualifying wager, I will get another four free at the same amount I bet (up to 50). I don't get the stake of my winnings on any free bets, but I would keep all winnings. It seems for this to work for me, all I need to do is win 1 of the five bets. I guess I would lose a couple bucks in fees to the site (vig?), but if I won two of the 5, I would be way ahead right. Assuming I have a 50% chance of winning each bet, this is +EV, right? Am I missing something? Anybody done this?