@Keegan Mattick
Hello Keegan - I'm a Realtor in Killeen and am particularly passionate about multi-families (I own a fourplex in Killeen).
I also happen to own two homes in Lawton, OK, myself, when I was stationed there (Field Artillery).
Just to understand - are you looking at living in either the fouplex/duplex you are looking at buying, and using a VA loan?
The VA loan has no downpayment and, at least in the Killeen area, it is often possible to get most if not all of your closing costs covered by the seller, meaning the $15,000 you have saved would just be for any repairs/upgrades that the seller wasn't negotiated into doing. However, if you already know that you are moving (PCSing?) to Lawton in June, a lender is not going to lend to you for an owner occupied building in Killeen. So presumably you would be looking at multi-families in Lawton, then.
If you are looking at investment financing, conforming loans are usually 20-25% down payments, meaning your budget would be approximately $60k with a $15k down payment (assuming again the seller can cover all of your closing costs), which may not be quite enough in our market to get a rent-ready duplex off the MLS.
I actually posted about this very topic just a couple days ago in my blog - house hacking, just like BP says to do! I wish I had done it with my first house in Lawton!