Quick Question about Project Management Platfroms...

Heres a quick question for the IH community. Does anyone know of a Project Management Platform (think Basecamp, Asana etc) that has a subscription function that team members/clients can sign up, pay and subscribe to?

Looking to use the platform in a side project :)

I clocked one on the net the other day but can't for the life of me find it again?

Can anyone help?