An industrial deck like the Panasonic AG-1980 would be a good investment, as it's built in TBC and video noise reduction can cope with all but the worst tapes. They are getting harder to find new though. Odds are if you stay in business long enough, somebody will approach you with a stack of Beta or 8mm videotapes. (When I was in college, people often came to the tv station seeking transfers to VHS, but we had to turn them away for some silly regulation! I could have started a business under the table had I been less innocent and more evil.)
I got a decent middle of the line Sony Betamax for off Ebay a couple hundred that works well enough for transfer purposes. You don't need the ultra-expensive high end Sony models with bells and whistles the collectors all chase. Avoid non-Sony manufactured betas like the plague! And don't bid on any Ebay auctions where the seller can't or won't test the deck they're selling. Sony did make 8mm decks, but a camcorder is probably easier to get at this point.