Even if you could raise the money, no bank will loan a large percentage of it, your largest hurtles would be zoning (allowable land use), adjacent use compatibility, and environmental impact. Even though a track is potentially nothing more than a long parking lot that happends to be very very loud on the weekends it's not an easy path to hoe.
I agree that 30 acres isn't even close to being enough land, unless your just going to build a cart or AX course. A decent new road course is going to be no less than 1.5 miles, ideally it would be around 1.8 to 2.5 miles. Large enough to have lots of cars without crowding but small enough to safely manage an event and keep costs low.
These days developers sell condos and other facilities and amenities on-site to offset their costs, think country club/golf course/resort.