This is from the Walk Through for the Support Program:
Note:
US Citizens or residents must return a signed W-9 form.
Paypal Accounts are required as all payments are made through Paypal.
(1/14/2015) The Support Program is currently in Beta and is only available to creators who have at least 500+ subscribers on one particular series.
The only reasons I can think of that may disqualify you are if you're under 18, or you don't have over 500 subscribers to one series. The program is in beta, so if you don't have over 500 subs quite yet, I imagine Tapastic will be more lax about requirements later down the line? Hope this helped a little!