I am in the Indian Health Service and an OB RN on the Navajo Reservation. There are two paths, the corp as stated above or civil servant (me). No age restrictions and not considered military but part of govt retirement system. The IHS has many job opening all over the country, pay is less than private sector probably due to pay scale being set by congress and you know how long an act of congress takes to change anything. No low census call off days though, guaranteed 80 hours a pay period which is way different than private sector practices. I worked private sector prior to IHS.