Here's the math:

Pot: $3. Villain bets $2. We call. Pot is $7. Villain bets $5. We call.

Now let's say that if my draw hits on the river (or the turn), Villain will not put in any more money.

EV= -$7 + (36/100)*$17 = -$0.88

So this is basically what we need to make up for should we hit. Thus (36/100)*x=0.88 or x= $2.44.

So we need to get atleast $2.5 on the river if we hit our draw to make this play +EV.