I've been watching this thread wanting to respond. Like so many, what I know about retail is from the consumer, not proprietor perspective. Based on his gentlemanly persona on this forum, I have no doubt that Jim was a highly successful shop owner.
That said, I cannot imagine wanting to open a train store in the 2020s or beyond, but also imagine it was a great joy in the past. The internet has permanently changed buying habits that don't benefit traditional retail. While I've NEVER been the kind to shop at a specialty store, pick their brains, and then run to a "big box" store to save 5-10%, I sense many do just that. Heck, I buy at least an overpriced water bottle every time I venture into a bike shop just as I always purchased something, even if just spare parts or track, when I visited the Trading Post Train Shop or when I now visit Stockyard Express. But, why settle for engine in a road name I don't want just because my LHS has it when I can find exactly what I want at a dealer with a website and shopping cart. No more local captive customer bases which has to hurt margins.
I've often wondered if two related themes in the 2010s and 2020s apply to future sellers in our hobby: (1) asset purchases are shifting to subscription services and (2) product manufacturers and distributors are looking adding post-sale value-added services.
Subscription trains? I don't know if that would ever happen in our hobby, but I see just about everything from women's dresses, men's ties and shaving supplies, and prepared foods being offered via subscriptions. Maybe some day we'll pay a monthly subscription, receive a refurbished, gently-used engine or what not, and return the one delivered to us months prior. Who knows?
Service? As a self-taught guy, I'd love to have a expert "consultant" come over from time to time, fix my mistakes and get me unstuck from my periodic drives into ditches in person rather than trying to explain my challenges on a forum. Yes, I'd pay for the service. Not sure this, either, will ever happen in our hobby, but it's happening in other industries.
Just my 2-cents.