.. But then you're also supposed to declare all purchases, even of used items, at the end of the year to pay sales tax on them.
No, actually. Though the specifics do depend upon the province/state in which one does business.
Here in Ontario, sales tax registration/collection/etc is not required on the first
(from poor memory here..) $30K of personal sales. Businesses have no such exemption, except for Sole Proprietorships.
EDIT: Oh, that was pre-HST. Things may have changed as of last year.. dunno.
Cheers