Setup payment page

I would like to create a payment page where users can login with e.g. an user account.
It should be possible to subscribe a payment (e.g.) paypal for a certain service (t.b.d.)
After the service is completed the payment should be done.
I am open to use existing websites/services to increase the safety issues (e.g. Wordpress)

My expectations
- Please try to set a realistic bid
- Experience with online Payment Services like Paypal
- Open for discussing different solutions/possibilities for the project

Please contact me for further details