By selling memberships of golf clubs, gymnasiums, library, etc. you add members to certain groups and provide them various facilities according to plans. While adding members to your plans you live in trouble with managing lots of hard copies of membership forms, customer’s information, their subscriptions, logs, expired subscriptions, etc. To handle it all effectively you will need Membership Management Software. See the proper software industry overview to get an idea quickly and take educated look at PayPlans - Members Management Software for Joomla under GNU/GPL license.