If Mobilized in support of a state mission, it is funded by the state budget, if for a federal mission, the federal government pays. That’s why governors are so quick to ask for a ‘federal’ emergency during a disaster.
IIRC too, the Federal Gov’t pays all or most of the bill for the maintenance and repair of vehicles/equipment and training of NG units. Additionally, I believe all the equipment is federal property. I’m writing this from memory so YMMV. A NG guy may have better info than I.
Cheers!