Hello Nicolette,

As note by your followup, I noticed that nobody answered. For someon to try
to answer, there are two big issues right from the start:

Your question s really hundreds of question, and some of them are in two
areas (inventory and invoices) where the business-process-defining and Access
work are amongst the largest and toughest.

Second, in order for someone to start trying to help you you will need to
describe the specifics of the process that you want to database. You
skipped this whole "useful infromation" part and skipped to providing not
useful information (your ideas in a few areas on structure).

This is a big project that you are embarking on. If you are willing to
spend a year of work and learning to get it done as a way to learn databasing
and Access more, then that's fine. If not, you might be better off looking
at some (small scale) enterprise softwar which would do all of those things.
..