Well, Selling online is not a hard feat, and i've done it many times, so that could stay with me, so it would be ssort of like ADG, as in, B&M and online retail.
I work in a pond store, and the paper work/computer work looks like a big part of the day's work.
As for inventory, obviously i'd need to keep some basics in stock, but for special order equiptment, i need not keep so much instock, that's the "special" order part, although i can see where having it then and there is a huge benefit.
At my work, we'll SO stuff for our customers and call them when it comes in. The same principles would apply to a petstore as far as i can see, i'd love to know my customers well enough to have their phone # handy.
RE: livestock
Alot of the stock would/could be bred either at my house, or in the store, ex: endlers, guppies, cichlids, killies, Dart frogs on occasion, plants can obviously be grown.
Other unusual stock will come from both hobbyists fine with the fact i'm making money off their stuff, or companies willing to sell their items for retail purposes.
EX: shrimp and dwarf crayfish.
If i could find a breeder of tiger/crs/RCS that would let me sell their items at slightly raised prices, then there would be my source for those.
Although it may sound bad bussiness, or arrogant, By NO means would i have things i am not intereseted in or interested in selling.
VERY few mammals,if any at all, or birds would be found at a petstore i own.
Same with their supplies.
I would hope to not be thought of as "competition", but more of "allies" by other shops, although i see this is thier choice.
Ok, i'm tired of typing for now.....