gridfree wrote: is it possible to have memberships based on disc space, anything difficult in having this type of option?

membership 1 150mb
membership 2 500mb
membership 3 1gig

thank you

With CBSubs you can create as many membership plans as you want.
Each user subscription can have its own duration and price.

You can also easily configure that each plan bumps the user to an extra Joomla user group.
This way you can use Joomla ACL system to limit access to specific site content and features based on their subscription.

I am not aware of any Joomla functionality (or add-on) that actually calculates/enforces storage quota per user.