[SumZero]

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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?

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It all depends what your true win rate is, what kind of plays you bet on (longshot moneylines, or spread bets), and what amount of risk of ruin you are willing to accept.

If we assume that you will always be betting $55 to win $50 and that this is the minimum bet allowed (so you can't move down if you are on a losing streak) then the risk of ruin if you pick 55% correct (which is +$2.75 EV per bet, a 5% roi) and if you start with $1000 is 14.24%. That's why most people suggest betting 2% or even 1% of your bankroll rather than the 5% you were suggesting. If we move to $2500 bankroll then the risk of ruin falls to about 0.7%. If we move to a $5000 bankroll then the risk of ruin falls to about 0.005%. Remember that this is with a 55% correct picks against the spread. If you do better than that then your ror is overestimated above. If you do worse than that then your ror is underestimated above (and if you pick less than 52.39% then optimal bet amount is 0% of bankroll). It is much more likely that you will do worse than 55% than better than 55%.

That said if it is just a fun amount for you and you can move down if you are on a losing streak then $1000 should be fine. And iirc only about half of the 14.24% of the time you were ruined did the ruin happen in the first 250 bets. So more than half the time you end up ruined you still make it through 1 NFL season of 10 plays per week just fine.