It really depends more on the Card Company. When the boys were young we collected everything but back then in the late 80's and early 90's. There just was not as many companies and brands and you could collect most everything. The other problem is when the boom hit, all the companies went nuts and there are tons of cards out there for most of the years. That drove down the prices.
We used them in card shows, and eventually as the boys got older. We sold all the Jordan, Bonds, Sosa, and etc for a new stove, fridge, living room set and then all of the kids into thier first vehicle. I just do not think for the most part that opportunity is there anymore.
My strongest suggestion is to get as good of info as to what brands of cards, and the sports and then see if he has the windows where the stud players of today would include thier rookie cards. That is where the money is. Once some of that info is in your hands. Go to the local card shop, or Barnes and Nobles and get the Beckett Magazines for each of the major 3 sports and start to
file thru the years of info as to what the sets of cards or individual cards are valued at.
Then remember if you have a good find, you will still take a big hit when trying to move them on the markets as shop owners and collectors will drive you down to a point of that they can turn the card for profit reasons. Unless you want them to collect for a long time, which is another matter entirely. Just some of the things you need to think about or plan for.
Yes it was good to buy all that stuff in a barter type enviroement, but trust me did keep just enough of them that I have
now given to my 30 year old kids as to remember a time we had, and to share with the grand-kids as well. Can be a lot of fun.
Also remember if you have a spouse if it is a lot of cards, storage, care, and sorting all become issues. My wife was really glad to see the last 12 monster boxes go back then. LOL
Hope this helps a little
SQUARE