Skip,
Thinking back over the flies I've bought the last two years, the list is really pretty standard stuff.
Woolie buggers - various sizes, black, brown, olive. Mostly size 10 & 12. Mostly bead head but also non-weighted.
Adams dry flies sizes 18, 20, 22.
Griffiths Gnats 20, 22 (would even buy 24's if I could find them)
Black and cream midges - 20,22 (would buy 24's if I could find them)
Stimulators - 12, 14, 16
Elk Hair Caddis - 14, 16, 18 (probably should buy some 20 & 22's as well)
San Juan Worms (red and maroon)
Various sizes of bluegill cork poppers
small clousser minnows
Nymphs (standard fare, bh pheasant tail, pheasant tail emergers, hare's ear, various scudd paterns, brassies, copper johns, anything that looks like it may catch a fish).

One tip, if you're thinking about going into business, there are two ways I can think of to make money at this.

One is to tie the staples. They are staples for a reason. They have caught fish throughout the years and fishermen buy them and use them.

Another way is to find some niche and specialize in some hard to find fly, some "secret fish getter fly" or some custom order stuff (i.e. fishermen can send you a photo of the bug, or a description of the bug and you can "match the hatch" for them on a quick turn around basis.

One method is volume and the other is higher margin.

I guess it just depends on what kind of money you want to make and how hard you want to work.

I hope this helps.
Jeff