Yep, everything they said.
The major expense for me was electricity. If I had spent a couple hundred on insuation before installing the tanks, I would have saved literally thousands of dollars.
tHE cONCH's idea with wastewater is a stroke of genius, It didn't take long for me to get sick of running the hose down the driveway.
I retailed alot of fish out of my fishroom, so one of the first tanks contained a couple of turtles that children *loved* to look at and pet while their parents were looking at fish.
If you are looking at a retail setup or regularly selling livestock, make sure that the aisles are big enough for a couple of people to walk past each other.
Lighting can be a major cost - I ended up using alot of CFL energy saver lamps, one over each tank.
We had individual heaters and filters in each tank. This meant it took 1/2 a day to waterchange the room, individually cleaning the filters as we went. A sump system would have been a good labour saver - harder to set up, but a great idea in the long run.
If you have the space, a work surface is a great idea also - this is the place you will be mixing medications, having a brine shrimp setup going, or bagging the fish.
Also, have somewhere in the room for storage. No matter how many times I put the lids on the tanks, the containers of fish food would always find their way into the water somehow.