Yes these are good suggestions. You will do either:
A membership script (PHP) as an embed for the page or entire site. It needs to be manage by you on your own server
A membership software on another vendor platform. You will designate domains on their system with an account.
An ecommerce platform with a membership plugin.
PRIMARY QUESTIONS BEFORE DECIDING
A. Will customers need to pay before receiving access?
B. Will paying customers need their own account? To manage email, subscription, etc.
C. How will you handle renewals? By calling you, email or will they do it themselves in an account?
D. How will you handle cancellations?
E. Access: Forgot username or password? Is this auto or will they contact you?
F. How will you limit fraud? Customers sharing access with each other.
Just a few key questions that can be a pain without a dedicated solution. Obviously, you want automation for as much as possible, and you can see how a script you manage, can be time consuming. However, software vendors aren’t silly, they know you need this functionality, so they charge for this stuff (Monthly).
I agree with @foxy and @Revolution, Webflow will handle the static part of the site, but you will need a script to trigger member access, because the site needs to talk to a live database before actions are taken on the site.
Hope this helps. If you need a list of vendors to get you started, shoot me a message. Take care.