Almost since Day One, there have been people trying to make money off the notion of comics fandom. Obviously, there were the folks producing comics content and comic distributors and all the people associated with making comics and getting them to consumers but there were also some who recognized that there was money to be had in catering to people who already had comics. Back in the day, they were few and far between. And I doubt many of those people were able to make it a full-time gig. The fanzines around EC comics are probably the most well-known examples.
Starting, I think, in the late 1970s, we start seeing a greater proliferation of entrepreneurs seeing the market potential in comics fans. That's when we start to see people producing long boxes and comic-sized bags and price guides and the like. Even the larger companies that worked on these projects did them in conjunction with another primary business. They made comic bags but really they mostly made sandwich bags they sold to Ziploc.
While I was able to see an increased attention on fandom was coming as far back as the 1990s, I had little clue the full extent that would take. And I'm certainly not prescient enough now to see where it's headed. Beyond perhaps a greater diversity through fragmentation and niche marketing. The key will be in keeping your eyes not just what's happening now but also where the fandom industry writ large is headed. No easy task to be sure but one that will almost certainly help to propeller some entrepreneurs to success in the same way that it's helped other risk-takers in the past.