i bought live rock from my local fish store, it was kept in water with a power head so it was kept live. i still cycled my aquarium for a week just to get all the dead bacteria out as well as used instant ocean bio spira and again let it cycle for another week. then when i bought my first round of live stock, i got two mexican turbo snails and a empty turbo snail shell for my hermit crabs, the empty shell had a spot of coralline algae on it, and before i knew it most of my live rock was covered in the beautiful stuff.
moral of the story is even the smallest ammount of established stuff will make the whole process that much quicker