Owning a plane is expensive, especially on your own. You have to factor in maintenance, insurance, annual, tie down/hangar fees, fuel...did I mention maintenance? You also need to pay for an instructor, so in the end I don't think it would cost much less than just going to a flight school and renting. Much less headache and stress than owning a plane.

My advice would be to get your ratings while you're in the military, pay as you go. Not sure if your schedule allows you to do that, even if it's training on the weekends. You may have to pay out of pocket, but it would end up costing you less if you get your training done at a mom-and-pop school as opposed to atps. Because 1 1/2 years before you start your IR is a long time. I mean honestly, you should be able to get your IR and Comm in a 1 1/2 years even if you just train on the weekends.