Paypal has two systems
Paypal Subscritpions and Paypal ARB (automatic recurring billing)
I would recommond not using them. Its a pain to develop with both platforms and you will have to. Paypal subscriptions is free (per trans fees), but your customers are going to paypal to make the subscription. Then you have to create an IPN (instant payment notification script) to handle subscriber payments. Paypal ARB lets customer pay on your site with a real merchant account, but requires that you offer paypal subscriptions to qualify for decent rates.
If its a legitmate product that will expect decent revenue i would:
1. Get a real merchant account.. FLAGSHIP Merchants are awesome.
2. Build an app that manages subscribers in a database
3. Run transacitons monthly thorugh authorize.net recurring biling profiles or though an online invoiceing service such as FreshBooks.
4. Use twilio for programming SMS (ifbyphone.com is a good resource too)