On a film production the job of the DP is not to file tax returns or chase clients for new business.
The job of a lone operator is 50% business and not all artists have that skill.
That's the choice/burden of any freelancer or business owner though.
I could kick back and earn a fat salary working on other people's projects and ideas.... and sometimes i have to, to pay the bills.... But generally i work on my own projects and accept that i will have to spend valuable time doing business stuff. The payoff is worth it though, as i get to make artistic choices without dealing with a client.
On the initial topic, if i were to get in debt over a camera, the 1D-C would be low on the list. I admire the camera, but it is about the least future proof 4K camera that will ever be released.
The F5 seems like the better bet and the system could be built up slowly, hiring the 4K recorder when needed, then buying it when 4K is mainstream. F55 even more so, if you have the business model to do it.