The first time I got my Live Sand from an LPS they had it in a tank specifically for develping livestock within the sand. I bought 25lbs of it along with 65lbs of live rock for my original start up.
I put the LS & LR into the tank around 5:00pm which was not cycled but had the right salinity and temp, and after the dust settled - it just gets murky for a while. I set my rock in places I wanted and turned the lights off. After dinner (about 7:30pm) I turned the lights back on and the tank looked good. I set the light timer to cut off at 9:30 and around 11:00pm I took a flash light out to see if there was anything interesting going on in the tank.
I was surprised to see a number so of worms, copapods, and tiny little snails, not to mention the mantis shrimp that came with the LR.
Bottom line - if your getting bio-enriched LR (stuff in a bag) you getting sand with a biofilter, if your getting Live Sand you may be getting a whole lot more.
I hope you get a whole lot of great little animals to get your tank started.