I agree with Phil Rhodes. If you have $15,000 to spend on a short, put it on the screen and not in a camera. You can easily rent any camera you would like to use, Alexa with a nice set of lenses etc and the gear you need to shoot, plus some knowledgeable crew for that amount of money. You could easily spend the $15k on a camera package and still not have everything you need for it. If you're not a working cinematographer, I wouldn't purchase something. I know the idea of buying seems attractive, you have a tangible item after you shoot and can re sell it if you want after, but you could probably rent and not spend the full $15k.
All I know is that before spending all your hard earned money, do a budget of renting gear and paying people first. If you are shooting all day exteriors you will mostly just need grip equipment that is cheaper than lights to rent as well.
Just do some homework first, good luck!
-n