Ron,
The Singer 206K is my Holy Grail of sewing machines at this time. From what I've read it was Singers first domestic ZZ machine. Was made in both aluminum and cast iron. It does take a 206-13 needle and those are still available from Schmetz as well as Organ.
I would take one in a heartbeat. But so far I've not found one I could get at the time I saw it.
If the machine is in good condition, with a reasonable price, I wouldn't hesitate buying it.
Joe