So basically I think you should try a very cheap router to start with as that'll be fine for making signs and other bits of pieces from wood, then you can re-invest the profits in getting a proper spindle and start cutting metals. Unlike the rest of the machine you don't loose much money by going for the very cheap option to start with and still have a useable machine.
I totally agree with this. I started off with the MDF, threaded rod and skate bearings contraption. Every body on here told me it was a big mistake and it was in the end. It worked ok, if you could call it working, but only lasted a couple of months. It was nice to cut some things and i did have a big smile when it first came to life. But i got frustrated with it limitations after a week or so. It all warped due to moisture etc, mdf sucks it up like a sponge. I'm now hopefully going to build a totally new machine using ballscrews, supported rails etc. The only thing i will reuse is the motors, electronics and the router. But the router will be changed for a spindle in the end. I probably lost around £100, which would have been better spent doing it right the first time. I'm still struggling with the design, nearly 8 months on that, but every one on here gives constructive criticism, i mean help. I believe you have a big advantage in that you can use cad to design etc. so listen to the guys on here and it will be right and right the first time.