the 3 best LFS in my area all sell the fish, coral, and dry supplies to set up and keep them alive.
as for guarantee on fish its usually 5-7 days and u must bring the fish and a water sample thats seperate from the water the dead fish is in. all 3 also write the date the fish was recieved next to the name and will not guarantee it untill it has been in the store for a week, u can buy it b4 that week is up but u do so without the guarantee.
also u should have a few large tanks for live rock, one brand new, one curing, and a cupple fully cured so customers can get rock to put right in there tank or get some with a lil die off to start a new tank cycle.
another LFS which is really a LCS (local coral shop, cuz thats all they sell) has a big tank that is 7'x7'x1', like a big lagoon for just clam, anemone, sps, and, acans. they also have a frag tank with peices for $15 once in a while they do a clear out sale 2 for $15!. i would sugest bringing in big corals and fraging them urself to make a lil profit.
good luck and i wish i lived near ya so i could go shoping sounds like u got a good plan