Setting up a one time payment

If I want a member to pay once for an information product and they can always gain access to the site once they have that product, how do I set that up?

I choose Indefinite

But if I choose one day the user only gets one day access and if I choose 365 days I receive a paypal error.

If I choose Serial

The user stays at that level but it is then renewed which I don't want.