At Transferum every each account has its own amount of space,based on your request.Into this space can point 1(one) or multiple users without any restriction or with restrictions setted on each user.
Let's take an example : there is the account A with 256 MB space.In this account have access 2 users.If there are no restrictions on each user user 1 can upload a file as big as 250 MB, so inside the account will remain 6 MB free for user 2. If this situation is suitable for your needs,than is fine.
We can create restrictions on each user, meaning that inside the account we can create 2 another folders, 1 for each user, and inside each folder each user wil have its own space pre-allocated.For example the Account can be splitted in 2 equal sub-folders for each user.
There can be multiple ways of splitting and sharing an account between users.
For any question contact email@example.com for offering solution at your needs.