Need to choose Db Platform- help!

I’m a newbie and while I have experience trouble-shooting, analyzing and fixing problems in already existing systems (hardware or software), I’m now faced with the new challenge- starting an inventory db from absolute scratch, and it has to have a twin db (which it would relate to) that keeps track of all our outside resources (suppliers, contractors, vendors, etc.) They both would be accessed by our sales staff who should be able to reserve our inventory (rental) and outside resources so thatno other sales person can promise them to a customer on the same dates. So, I’m guessing a third scheduling db is needed to tie the other two together… nevermind that there’s talk of wanting barcoding for inventory.. anyone have suggestions as towhere to start?