Sorry to pee in the Cheerios, but this situation reminds me of cold calls from stock brokers that I get all the time at the office and my response to it: if it was that easy why would you be calling me to buy 100 shares of stock?
Finds are finds because they are rare. You have to really luck out to find a horde of T206s, and they are much more likely to be found by someone who knows someone who is affiliated with an auctioneer or dealer, aka a warm referral.
https://www.sportscollectorsdaily.co...oldin-auction/
https://www.sportscollectorsdaily.co...d-judge-cards/
What is being suggested here is a business model that is at least 20 years out of date. Rosen had a fit over the entry door to the IX Center but his act had been in decline for a long time before that. Everyone set up at a show is looking to buy and everyone has wads of cash. Adopting Rosen's shtick won't cut it. By the time someone walks into a show, they have already done their homework on where to sell cards. The cost of obtaining information has fallen and the ease with which it can be obtained has risen to such an extent that no proverbial widow or orphan is going to walk into a show and hand you a shoebox of 1952 Topps Mantles. It just doesn't happen. Most of the true collection buyers are mobile and advertise heavily online, because a search engine is the first stop for nearly everyone looking to sell off cards they found. I know several of these very successful dealers and they all have web sites, large eBay presences, and travel extensively to go to the cards. I also know a few whose M.O. is to hit every estate sale, miscellaneous auction and flea market. They grab whatever they can find opportunistically, and they do it consistently and pretty much full time. The rest of the collections go to auctioneers because they too have a heavy advertising presence and will travel with big money in hand.
What you are more likely to get as walk-ups at shows are modest groups of lesser cards that can be profitable provided you make a buy at the right price point, but that will not make you a fortune and will not cover the cost of a bare table. You also cannot pay 70% of market on 99% of stuff, unless your plan is to lose money and go broke. Sure, you can do it with a 1952 T Mantle but that is not the walk-in, for the reasons listed above.
You would be better off starting with Craig's List, flea market calendars and local estate sale listings than trying to wade into a room of competitors at a local card show. Try to intercept the opportunities
before they get to the door of the show. If you want to use a show, don't buy a table and wait. Hit the parking lot and entrance areas instead before the collectors get in the door.
I am working on a column about this; should be up in a week or two.