I would contact DRT Racing to see about a TaG Master package for you. They are an importer for the DR Racing Kart. They have one shop in New Hampshire and race team is based in Tennessee. TS Racing in Florida will also give you an option for parts and support during the winter months.
Another option for NHKA is the World Formula class. You can be competiive with a lower initial budget – buying a used kart with the engine around $1000 I believe.
Contact Keith Buffo for more specific questions about NHKA. Great person.