I live here.. But Birmingham, AL is in need of a good shop in the Richest part of town.. on the Highway 280 Corridor Between 459 and Chelsea. We have two or three shops around here.. And they are pityful .. VERY pityful.
We had a Sounds Great, it dropped in 2007 or so with the recession.. and a Tweeter which dropped everywhere.. used to have Circuit City.. went a long time ago.. so there's no High End Store Front with good solid, professional staff around here. And the area I outlined which includes Mountain Brook, Inverness, MeadowBrook, Brook Highland, Greystone, and Highland Lakes (+ more) has the most money in the state hands down. Cost of living is reasonable.. ie: Nice house for 2-300k.. Average house for 150-200k. In low crime areas. City of Greater B'ham population is 1.3 Million.
Otherwise,.. my first thought was LA,.. I'm sure it's a saturated market, but if you can make a name for yourself you get business,.. but Celeb endorsement probably makes or breaks people there and cost of living is astronomical.
The Mobile Audio and Tint is a good idea. Though becoming known wouldn't be easy. I still like places with a solid brick and mortar Store.. I miss that since all the Car Audio shops closed a few years ago here.
Good luck,