So are you considering coming in as an RN, or not until you are an NP or a PA? There are many different avenues. Service will give you access to the GI Bill: Welcome to the GI Bill Web Site | The Home for All Educational Benefits Provided by the Department of Veterans Affairs
. There was tuition assistance ($4500/year) for service members, but that has been suspended due to the fiscal crisis/shenanigans (I believe it has been suspended for all branches; I'm in the Army, and I know for sure we don't have it right now
In the PA realm, there is the IPAP program: U.S. Army Medical Department Center & School Portal
The Army also has something called Long Term Health Education and Training (LTHET) that nurses can apply for. You're paid to go to school and earn your MSN or similar, and I believe they do have some NP programs under LTHET. A degree through LTHET will earn you a longer active duty service obligation, i.e., you have to serve a certain number of years after finishing. LTHET is (understandably) extremely competitive, as is the Army Nurse Corps as a whole right now.
Good luck, whatever you decide to do.