The trivial solution is to tie residency to property ownership or property lease, and payment of property tax. Then use the prop tax to pay for the health care

The trivial solution is to tie residency to property ownership or property lease, and payment of property tax. Then use the prop tax to pay for the health care, because almost all health care is local anyway. Have the hospital or clinic or whatever bill the municipal taxing authority wherever you live; for most people the house you live in. Determining residency is not rocket surgery; could steal the entire system from state income tax codes.