Memberships are hardER to sell.

So I would not recommend you use OTO's for selling memberships. Infact if it is a membership program, why bother with an OTO?

Give them first month membership free as a bonus with your product which is just the BAIT to get them on your member's list! And ten tell them that they can cancel anytime within the 30 days if they don't like to continue! If they wan't to continue, they have to do nothing and will be billed after 30 days.

Cool!