You can use member usergroup sponsorship to let people purchase special powers (which might include the ability to add more articles than regular members or access special sections of the site). Usergroup sponsorship can also be used to promote all articles owned by the sponsor to a special priority type, if desired.
To get started, create your privileged usergroups with the desired permissions at Admin Panel -> Members -> Manage Usergroups. A "Sponsor" usergroup exists by default for this purpose, but you can modify that or create more sponsored groups. If you want to require everyone to pay to register then you don't need to create a usergroup as you'll be using the "Members" usergroup.
Now go to Admin Panel -> Revenue -> Sponsorship. You can use any of the supported payment processors -- PayPal, authorize.net, 2checkout or nochex -- or you can leave all three of those fields blank and process payments manually (via Admin -> Revenue -> Add Offline Payments) after inserting your desired payment processor button or instructions in the sponsorship template (Admin -> Themes -> Manage Templates -> "Sponsor Purchase - Usergroup").
Click the "Add Usergroup Sponsorship Level" link at the bottom of the sponsorship page to add a level. Follow the instructions on screen. Important Note: for 2checkout the item number must be the same number as a corresponding product you set up through the 2checkout interface that has your desired price and an approved URL of WhereverYouInstalledWSN/2checkout.php .
If you want to require all registrations from non-admins to be sponsored, just create a sponsorship level which promotes to "Members" (you can have them revert to guests or to another usergroup you set up for expired members with guest-like permissions). Otherwise, set up a sponsorship that promotes to your special group and demotes back to Members when it expires.
After you've set up a sponsorship level you'll see the levels you've created listed on the sponsorship settings page for you to edit.
You can customize the payment buttons and the rest of the payments page at Admin Panel -> Themes -> Manage Templates -> "Sponsor Purchase - Usergroup".
You'll find a link to membersponsor.php asking your members to sponsor has appeared at the bottom of pages. This is in your wrapper template. You can modify or move or copy it to anywhere.
If you wish to have certain content only visible to your sponsored usergroup, you can use a template conditional in any template:
This is only visible to people in usergroup #5. You can find the usergroup numbers on the manage usergroups page.
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If you wish to make entire pages inaccessible to people not in the sponsored usergroup, see custom permissions restrictions.
If you'd like to make a toplist of articles submitted by sponsored members (for display in a showcase or the like), go to Admin -> Themes -> Toplist Generator and use the filtering condition usergroup=5 (change 5 to your sponsor usergroup number). You can also show articles from multiple usergroups using usergroup=5 OR usergroup=6, for example.
Changing Sponsorships
As of the 7.0 series, sponsorships changed from being funds-deduction-based to being date-based. When someone sponsors a article, their account gets promoted and an expiration date for the promotion is set. Changes to sponsorship settings won't affect the expiration date. This means you're free to alter the price of a sponsorship level without affecting already-sponsored users. Once the account comes up for renewal, however, the owner will have to pay the new price to re-sponsor it.
Member Sponsorship Template Variables
These member template variables are related to sponsorship:
{MEMBERISSPONSORED} - Checks whether the member is sponsored. Use in a conditional.
{MEMBERSPONSORENDDATE} - The date their current sponsorship ends, if applicable.
{MEMBERSPONSORLEVEL} - Their current level of sponsorship, if applicable.
Notes
To test paypal using paypal's sandbox, see Testing Paypal Payments.