I am looking forward to buying a VPS but currently I can only afford to buy an unmanaged VPS.
How can I manage it for us with email and web hosting?
Depends how much management is required. If you need to install the OS yourself, forget it. If you just need to set up the websites, add domains etc, it's all relatively easy with Plesk control panel.
Doing a simple Google search turns up a bunch of info. Try these:
Do that search and you should find something in the 2.8 million hits you get.