What will people sign up to do on the website? Shop on your site? Sell their own products on your site? List their businesses? Take a course? Access locked content?
Or do you just want to have a database of some offline membership (ie no activity on the site)?
So basically the signup will come with the regular account for the person who paid, plus a number of additional free signups, lets say “5” additional signups
You’ll need a WordPress “membership” plugin to protect the content and provide access based on user subscription, manage subscribers and subscription plans, allow signup and payment, handle recurrent billing, etc.
There are a whole lot of these plugins out there: both free and paid. You’ll need to check out a couple of these to see which one will best serve your needs:
https://ww.wp.xz.cn/plugins/search/membership/
So basically the signup will come with the regular account for the person who paid, plus a number of additional free signups, lets say “5” additional signups
This is the tricky part… and will very likely require custom coding on top of whichever membership plugin you choose to use.
Good luck!