The businesses not eligible are the "sin businesses" listed in the statute; there are also businesses that are just impractical due to other statutory requirements (financial businesses, investment enterprises, triple-net leases of real estate, holding companies with intangibles, and the like). QOZBs have their own statutory and regulatory compliance regime, so you do need to make sure you follow the applicable rules, but starting a QOZB is just a matter of forming a tax corporation or tax partnership with the proper language in the organizing documents.