Hello!
While I'm not applying for the HPSP program, when I was in the military I shadowed a Army Vet who did. This is the advice she sent me in an email.
"Most Veterinary Corps Soldiers sign up very excited thinking they will do 20 years, and then become disillusioned within a year or two and leave as soon as their 3 year active duty commitment is up. But a few really love it and attach to the Corps and never want to leave. The ones that want to stay love the Military more than they love being a veterinarian, because being a DVM is only a part of your duties and the longer you stay in, the less veterinary work you do.
The pros are the privilege of serving, working with Military Working Dogs, getting paid to do Soldier things like weapons, PT, etc., and being a part of a cool group within the Military. And of course paying for vet school.
The cons are that you worked so hard to become a vet but then your time is so divided between veterinary care, public health, food safety, and Soldier duties. You do a day of appointments, then the next day you are inspecting the Commissary, the next day you are driving 3 hours across the state to inspect a bottled water plant that sells water to the Military, then next day you are at your weapons qual, and the day after that you are investigating a dog bite on base for the rabies program. If you just want to do vet med, the Army can be really frustrating.
The Army also puts you in charge of a vet hospital right away at your first duty station, even though you are a new grad. So you are forced to step up and be confident and be OIC even though you are a new grad vet. A lot of CPTs really flounder in this position.
And of course there is the usual cons of no control of where in the world you are assigned, and the Army treating you like a child even though you are a doctor.
Oh, another con is that you are on call for your working dogs 24 hours a day always and must remain within 30 minutes of your dogs at all times. You can never relax, and never do anything fun on a Saturday more than 30 minutes from your working dogs. It can be a long few years.
I am proud to have done it, and am financially free because of it, but I have never missed it one day since the day I drove away.
So there's the run down for your friend. Good luck to them!"
As always, experiences will very but the military is a unique beast. I was happy to have served and gotten the benefits that come come completing an enlistment but its not for everyone. There are many, many times in the military where I was dumbfounded at how things were ran and towards the end it became almost unbearable. Take everything your recruiter says to you with a grain of salt. Be ready to just go with the flow and understand that so much of your job could have NOTHING to do with vet med.