Paywall for whole webiste

I am looking for idea / solution how to handle Paywall system on my website.

• Whole website must not be accessible for visitors, registered users only can see everything
• Whole website will work for paid members only. You pay monthly / yearly subsciption, you can access site. Without active subscription you will see only login / payment from
• Bots and Crawlers must be able to access site to not broke SEO
• How to handle membership system without any additional plugins? I have Fluent CRM free version, can it be handled by this plugin only with user tags? Or is it necessary to have something like Paid Membership pro or something similar?
• I would like to use Fluent Cart Pro to handle all payments, reminders for expiration etc.

Any ideas how to make this system easily and realiable?