I don’t think there are any restrictions, but there are features that are not in the home edition, that you may need in a commercial environment. There is a comparison table for Vista, on the Microsoft site http://www.microsoft.com/windows/windows-vista/get/anytime-upgrade-compare.aspx
The main thing missing from home edition, that you will probably need, is the ability to join a domain, which is only in Business and ultimate according to that page.
I guess you can look there, and if Home has all the features you need, then save some money and buy that (but if you really want to save money, use Ubuntu and forget Windows).
I hope that helps.