With a pay league, you want a payment deadline that is well in advance of the draft to account for this very issue. If someone doesn't pay by the deadline, then you'll have to find someone else (or give them an extension if they just forgot or whatever). But, if you wait until draft day to collect payment, then you're just asking for trouble. How many are in the league? If it's only 2 people and they don't pay, you could always just run the league without them, assuming you've got at least 10 other people involved.