As I ponder this question, not as a cigar store owner but a customer, although another type of business owner, I would say that your biggest competition is gonna be the Interweb...there's just no way you're gonna be able to compete with some of the prices out there. How does a B&M overcome that? With superior service. As simple as that. Engendering customer loyalty.
Tell ya a true story...when I moved to my current address, I was excited cuz there was a 24-hour B&M combination cigar store and newsstand just a mile from home. I was paying somewhere in the $10-12 range for cigars, I'd pick up 3-4 a week, no need for humidor. About a year ago, I discovered a few of the on-line major sellers, and found out that I could pay $2-4 a stick! Well, hell, the heck with the B&M...I had really never felt that they reached out to emphasize customer loyalty...never saw the owner there, just his minions, and they couldn't care less. Then I began to notice that the magazines that I like weren't getting restocked timely, and lately, I've noticed many empty boxes in the humidor. Ooooopsie! Not a good sign...either that the store's management is particularly solvent, or that anybody cares to keep things restocked.
Some businesses don't compete with the Interweb...your proposed business will go head to head. Be prepared to overcome that, somehow. I'll leave you to figure that out. One of the better ideas is several years ago where a young man rented a very small space from the City, my hometown...this space was adjacent to the downtown theater, and was like 20'X10' max....VERY small, but ideal for a humidor, but the proprietor had to sit outside. He was open limited hours, but that was okay...as long as you could depend on that. He was a member of the volunteer fire department, as well, and before too long, he'd open up, get bored, and go down the street and around the corner to the fire department instead of minding the store. You'd go to the store, find a note that he'd be back in a few, you'd wait a few, no show. So, off ya go! Didn't take too long before his business failed.
The most important hour of any business catering to walk-in business is the first half hour and the last half hour of the business day. Arrive ON TIME...or early...and close up ON TIME...or late. The outfit that supplies parts to my own business failed in that miserably...the proprietor would frequently close up an hour before normal closing time...no notice...and finally, a couple of weeks ago, I just totally started ordering parts on-line. Easy peasy. No wondering if they are gonna be open. Get home from my regular part time job, parts are waiting.
Word to the wise...you can't be lazy. And a business owner works 24/7/365.