By all means, check out whether there are used ones available in the boating
community. However, CPT autopilots had a significant upgrade in the last couple of years with a redesign of the compass
assembly, so you might want to consider asking CPT for an upgrade to the electronic compass
assembly if you buy an old one. Check out their website.
An alternative might be to call Jeff at CPT and explain your situation and ask whether he has come across any good used ones. He and his wife are past cruisers and we have found them to be very reasonable people. When we were researching CPT's we visited Jeff's workshop on their property and since then we have cruised a year with a new CPT on our 22,000 lb Coast 34 sailboat.
We could not be happier with our quiet, reliable, energy-efficient CPT. For long-distance passages, however, with sufficient winds we use our Monitor windvane
, as it will steer for many 24-hour days with no power use at all. Coincidentally, at one point CPT's were produced by Scanmar, the company that produces Monitors.