I'm doing some heavy post production work on a stopmotion film. It's a personal project, so I don't have much budget, but it's so heavy that it might save me time (and time is money) to do so. I'm currently working on:
Buy a used tower then sell it for what you bought it for when you are done. You shouldn't lose any money and if you are lucky you might even make a few bucks. I know this for sure you will definitely not lose 600 for 2 weeks unless you fire sale it off. This is if you can front the money until you can recoup it several weeks later.
I actually ended up doing this. I bought a top spec iMac refurbished from apple (it was £350 less than the new price) I figure even if it drops another £300 when I sell it (about 30% depreciation from the new price) then I'm still in the same position only I can keep the machine for months rather than weeks. I may even just keep the machine entirely if I can. Good to get confirmation on this way though.