Expected variance in sports betting?

[The Don]

How many units is a safe bankroll for making something like 10 NFL plays per week at $50 a play. I expect to be +EV as I will do a lot of following Fezzik (and a few other talented bettors) and making one or two of my own plays each week. I realize that I can always lower my bet size if I hit a bad streak. Hypothetically though... if i had to make $50 bets every time what do you think would be a safe bankroll for my situation? $1000?