I run my business with aMember.
aMember is software installed on your own hosting, so you pay a one time fee for the license. ($189.99) You then pay $80 per year for Upgrades/Tech Support Availability.
Other options like 1ShoppingCart and InfusionSoft involve software hosted on the sellers server. You may a monthly fee for ongoing use – and a sizeable set up fee in advance.
aMember does not have the best client documentation for non-techies. For this reason, Lynette Chandler and I created a detailed video course that teaches newcomers it's use. From set up to making it sing for it's supper, we cover it. Check it out here.