all of my buddies that do ride have said you can learn the same things form an experienced buddy in a parking lot and save the cash for some safety gear
statistically learning by yourself is less dangerous than having a buddy teach you, most likely because you will take it slow and a buddy will rush through things. (according to the Hurt report, yeah, yeah, i know it's old, but it's about all we have to go on)
I am a HUGE advocate of the MSF/BRC and the ERC and whether you are new to the sport or back after a five year hiatus, you will learn a lot more than your buddies can teach because usually what will happen is "here's the gas, here's the brake, here's the clutch...now let's hit the road".
Do everyone a favor and buy good gear even if you didn't save any money by having your friends teach you. The cost of the MSF/BRC can range from under a hundred bucks to around 300 on the high end...which is probably one of the cheapest bits of safety you can buy honestly.
if you are looking at a katana 600 you could always put some decent frame sliders on there. I wouldn't recommend it as a first bike, but there are way worse choices.
Not being in the military i am not sure, but, there may be some rules that you have to take "officially sanctioned" riding courses to be able to ride on base or to ride at all, so you may want to look into that before you decide.
P.S. thanks for serving your country /salute