I take my pups at about 4 or 5 months, but of course I do'nt expect them to do anything till 7 or 8 months. But the pup I got now is almost 6 months and is starting to run. she jumps lots of rabbits and starts them, but the bigger dogs always run off with it and leave her.
I started taking them out with me when running the other hounds as soon as they can keep up with me. They try and run with the hounds at about 4 months, but before that, they have learned how to get through the brush, over fences, cross creeks and so on. It seems to make them start alot quicker too. My bud Kansas Mike taught me this trick, I was always using a starting pen at about 6 months, and Mikes were always running already, so I started doing what he was doing and it has worked out great.
I start mine at 10 weeks in a eye sight pen to get their interest up, I do that about once every two weeks for about 30 mins each time until they reach 4 months of age then they go with a single or two dog pack.