There are times that I think magic shops (and their inclusion or exclusion) are one of the more controversial aspects of a campaign.
If you have one (or more) it makes magic common and no longer as special. If you have none, where do the player's sell off their excess magic (assuming they have any) or spend their gold in bulk?
I have no problem with the apothecary or scrivener adding an occasional permanent magic item to their inventory of wares, but I shudder at the idea of magic shops popping up like used car sales men:
"This here wand of fireballs was just used by the mage Bobulast to clean vermin out of his storage cellars. Hardly been used. Command word? Oh, that's an extra 50 geld."
If I did have a magic shop, I'd want it to be more like an antique shop with perhaps an anti-magic effect over the shop, preventing items from being misused against the proprietor.
"That there is a rare piece. One of a kind even. Look at the patina on that blade, shows it's age and it's heritage it does. You'd want to leave the patina. I wouldn't clean it more than a slight buffing or you'll ruin it's value. Yep, might only be a blade of minor power but it has a history well worth it's weight in gold. Er, careful with that snow globe. Iffin it drops we may find ourselves in the midst of a snow storm, magic protections or not. Remember, you break it, you bought it."
The Minotaur for Old-School Essentials
*Requirements:* Minimum STR 9, Minimum CON 9
*Prime Requisite:* STR and CON
*Hit Dice:* 1d10
*Maximum Level:* 8
*Armor:* Leather, including shield...