It's like the car business. If you're able to front the money it can be profitable. Like recently I bought an average complete 1957 Topps set cheap needed work. I'll replace probably 100-125 cards or more (407 card set) for various reasons. I'll take the star cards Mantle, Clemente, Mays, Aaron, etc. I have in the set and get them graded or buy better graded cards selling the cards I don't use. I'll spend 3K over a year or so and then have a set I can sell for $12k or more almost doubling my money. Finding the cards for the right price is the fun part for me online bids, online sellers, card shows, they're out there.