Looking to Buy Live Sand

I would suggest starting from scratch on sand. Just too many problems that could come from someone else's old sand. I don't think it's worth the risk for something relatively cheap in the scope of the hobby.
They sell stuff packaged in a bag that is supposedly "live", but I'm not real sure how much benefit you get over just dry sand. I think to seed the tank some live rock from a clean and trusted source would be more beneficial than sand.
I used Dr Tim's one and only bacteria and pure ammonia last time I set up a small tank, then just waited out the bacterial cycle. Seemed to work very well, and absolutely no chance of adding anything you don't want into the tank.

 

I haven't ever really had big problems with re-using sand as long as it's rinsed well. And by well I mean about 1g of sand in a 5g bucket, full pressure spray with a hose nozzle to churn it up, pour off the water, repeat until clear (usually 3-4 times). Then repeat 1g of sand at a time until you're done with it all. Take a while but you are usually left with pretty useable sand.

 

How big is the tank? I'd be cautious of adding 4 clowns to a tank. Maybe if they are all really small and very similar sized. I don't think you want any larger, dominate female in there with several other smaller ones. Clownfish can be pretty territorial and aggressive little guys.