To verify the credit card is valid before creating the subscription you need to do an AUTH_ONLY for either $0.00 or $0.01 depending on your processor's requirements. If it is approved, and the amount is $0.01, you should then void that transaction. Then you can go ahead and create your subscription.
There were some rules changes and AUTH_ONLYs for $0.01 and I am not 100% up to speed on them. But from what I understand, Visa and MasterCard wanted to do away with AUTH_ONLYs for any dollar amount. They wanted merchants to use $0.00 instead as that leaves no frozen funds on a user's card and makes the purpose of the AUTH_ONLY clear. Definitely contact the merchant account provider and see what these rules are and what their level of support for $0.00 AUTHs are.