Which extension do I need?

I have a client who needs the following and I wonder if you could advise me which extensions I would need to achieve the following:-
1. User registers for a new account or if they already have an account they log in
2. They press a button to create a new licence for the use of an online design software.
3. Pay for this licence through Paypal.
4. After the payment has gone through it will update their account in the database and store the expiry date of the licence.
5. When they log in through the app, it will check expiry date stored in the database with the current date and if it is expired they will be directed to the payment gateway.
I would be grateful for any pointers.
Many thanks Denys

At the very least it sounds like you'll need to use either the User Registration Solution Pack or Security Assist to set up the registration/log in functionality, eCart to set up the transaction and DataAssist to handle the database manipulation.

I do have security assist but have never used it. Is this better than the User Registration extension

User Registration solution pack is set up for you, so you just have to put in specific information for your website and add some code to your pages. SecurityAssist allows you to customize the security more than User Registration Solution Pack. It all depends on what you're looking for.