Category restricted access by IP

You can add a password to any of the pages or posts you create if you wish.

If you’re wanting a full fledged Membership site you would probably need to purchase / or build a plugin to handle it.

You could try using Buddy Press and bbpress to create a ‘forum’ type situation and restrict access to the forums via the plugin which is free, but it does not restrict content created in the main site.

Or you could go with a Membership plugin suite like the one WPMU Dev offers that gives you complete control over everything you offer your members…

https://premium.wpmudev.org/project/membership/?ptm=b&utm_expid=3606929-108.O6f5ypXuTg-XPCV9sY1yrw.1&utm_referrer=https%3A%2F%2Fpremium.wpmudev.org%2Fprojects%2Fcategory%2Fplugins%2F%3Fptm%3Db