from a financial aspect, I don't see much upside to having a shop...back in the 80s through mid 90s there were a ton of shops throughout the area (at one point there were 2 in the neighboring town of 5000 people), and you could get packs at several locations (I lived in a town of 1200 people), and there were a variety of packs, especially early/mid 90s, now packs aren't easy to find, unless you want searched stuff or topps retail...
I don't buy single packs ever, just by the box or by the case, because there are so many hit pack sellers and people weighing packs, I don't even trust shops these days...sure, back in the 80s and 90s, you would get the cello or rack pack that had the guy you wanted showing on the front or back, but that isn't really 'searching' like they do these days...
you are also competing with online sellers who don't have the overhead, so unless you are selling VINTAGE stuff from the 60s or older where condition makes hundreds of dollars difference and you wont get top money for the card on an eBay or such site, or are selling knock off jerseys that you can get from China for $10 and sell for $40, it isn't really worth it I wouldn't think...
I drive around 40 miles to go to a shop, and the only thing I really buy there is storage boxes because places like blowout and dacw no longer sell them...
ive had people tell me I could open a shop, and I probably could with the volume of cards I have, but its a losing venture, so unless you are running it out of your home or already own vacant retail space and want to have it open on weekends or after you get off work from a real job I couldn't imagine doing it...
look at eBay, you can get say 40 autographs for $50 shipped - to resell in a shop, you probably need to get $150 out of them to even think about profit, but how long is it going to take you to move 40 common autographs? on eBay as a decent seller in good status, they give out free listings all the time, so at 20% markup you start making money, so anything over $1.50 per card average I can make something off of the cards, but with rent, utilities, insurance on stock, and potentially an employee or two, you likely have to charge $3+ per card that to break even...
since you have to buy in bulk to save money, how long are you going to be sitting on a 'dead' product. when regular topps baseball comes out, it costs what $50 a box give or take? so you buy say 4 cases to get a discount, but there isn't a ton of love for the product, so you sell 6 boxes the first month, leaving you with 3 1/2 cases and the next product releases, now the topps that you paid maybe $35 for and sold a few at $50 are selling online for $30 and people have moved on...
I see it when any product releases, in football, it was Press Pass that would have the first college cards so people would flock to it, then Prestige would come and no one wanted Press Pass, then Elite and no one cared about Prestige and it just continues...now if there isn't a 'stud' in the product you cant give it away...at the 2007 National, before Aaron Rodgers got the starting gig, boxes of Bowman Chrome football could be had for like $22 a box, no joke, then by 2010 Rodgers is established, those boxes go for what $50-$75 or so? so now they are worth what it likely cost to buy them originally...
I look at my Topps Olympic love...I bought 1 Hobby Box when the price dropped to $50 (initially retailed for $79+), I just bought 3 cases for under $24 a box, and that is in under a year. It originally released in November/December 2013 and 15 months later it has lost 60%+ of its value...
then if you look at the singles market, get caught holding the bag on a guy that gets injured/arrested...as a shop, you need to have some high end stuff, Ray Rice, Adrian Peterson huge drops in the market this year, when Jeremy Lin got hurt his National Treasures went from $15,000+ to $5000 in about 2 weeks, because it takes time for the market to adjust, can you take multiple hits like that? Its not like you dropped $20 a card into some Caleb Hanie cards that are a buck, you lost $10,000 overnight...
I play the risk/reward game, low risk, high reward, peddling 'junk' singles online...