it's tough to make very much money in the NFL since there are so few decisions. The only upside is you can bet pretty much whatever you want. But even if you can hit 56% over the season, averaging say 5 bets a week, you'd only end the season up about 7 units.
A small run of bad luck in the NFL can ruin a season's profits, whereas in other sports you'll easily rebound by the end of the month