Just about every cigar store with a walk-in humidor in my area carries a full-line of Altadis products and a few General cigar products: RyJ, Montecristo, Saint Luis Rey, H. Upmann, Gispert, Henry Clay, Trinidad, Vega Fina, Cohiba, Casa de Garcia, CAO, Macanudo, La Gloria Cubana. Throw in Alec Bradley, Ashton, Brickhouse, Excalibur, Fuente, Hoyo de Monterey, Joya de Nicaragua, La Aroma de Cuba, La Aurora, La Flor Dominicana, My Father, Onyx, Padron, Perdomo, Punch, Quorum, Rocky Patel, Torano, Tatuaje, Acid, Java, Tabak Especial. Include cigarillos and small cigars made by those brands...toss in a few of the super premium lines from those marques and the store will be able to satisfy just about any cigar need. As for boutique cigars, he should wait until he gets a solid number of steady customers who "call" for certain stuff before committing to sell them.
Suggestion: look up Total Wines and More on-line (most cigar smokers drink alcohol and look for bargains. This chain of superstores has a walk-in humidor about the size of your local's and seem to sell a lot of cigars at prices a little below the average B&Ms in the area): look for the store location nearest you, check their cigar lines and sort by most popular. That'll give him some idea about what sells best in your neighborhood.