I don't believe there is a Secured biz card offered by Discover. They have the one Business cc. There are personal secured cc's but they do not report to biz credit. There are a few secured biz offered like BBVA and Wells Fargo. You'll have to do some research for the few that are offered.
But if you are interested in building your credit in order to apply later for the biz then, "Yes" Discover has a great one. Look around the forum on the graduation threads, you'll get a feel for it.
Try all the pre-qual links you can. Including the Biz pre-qual links.