Anything special I should know about I5 computer usage for inventory, business use?
Nope. Currently any new PC system is robust enough to handle standard office work. - spreadsheets, documents, databases, email etc.
Higher end systems may be needed for graphics intensive work, e.g: Video/Photo editing, AutoCad.
Personally I'd stick with Windows 7 for an OS if you have the choice, FWIW.