The PayPal Group Subscription
PayPal Group Subscription extension is pretty good.
Using that extension, new members could go into a 'free members' group which aren't able to post and can only see 'lounge' topics.
Then they can pay to subscribe to a group which allows them to see everything, like 'full members'
Users will be automatically removed out of the 'full members' group on the day their subscription ends.
I also think there was an extension that deletes certain members automatically, can't remember the name but that extension could have been configured to automatically delete members out of the 'free members' group after x days, which would mean you wouldn't need to bother deleting members who didn't pay as it be done for you.
Alternatively, a simple way without using any extensions... you could disable all forum registrations and just design a fancy home page at
http://designsbydiebolt.com/, which tells users about the forum and has a payment button on it.
The payment setup would tell them that when paying they must specify a desired username... and then when they pay, you just create an account with the username/email they provide and email them the login details - with a random password and tell them to change it when they first log in.
Most of us will enjoy Christmas in the comfort of our own homes this year, however, sadly, that can't be said for people in the Ukraine who are suffering day after day, due to the Russian invasion.
If you would like to make a small donation to help Ukrainians in their time of need, you can donate to help all Ukrainians via
BritishRedCross or you can donate to help the Ukrainian children via
Unicef.
Thank You