Take 2 wires and twisted them together with a drill!
Ordinary telephone cord? The stuff I see around the house isn't twisted.
A quick read on RS485 at wiki says that '485 uses differential balanced lines rather than the twisted pair.
I haven't tried RS485 directly. I've done similar with RS232, a couple of 7404 inverters and some CAT5 ethernet cable between the house and the garage (about 270ft) and it seemed to work just fine.