Omega C760 worth considering
I had always used Omega D2s but when I went to put together a darkroom after 40 years prices were climbing or the shipping was outrageous. I wanted a Beseler 23c for medium format, but I was either offered machines trashed in schools or good machines in the $300-500 price range. I found an Omega C760 for $30 at a tent sale, and with a little scrounging on ebay and elsewhere (haggle, because these are not real popular for reasons I will explain) I got a complete set of light diffusers, a condenser head, all the negative carriers from 35 mm to 6x7 glass (which I need for oversize enlargements) extra bulbs and even an Omega Simtron darkroom exposure meter, which is unnecessary but looks way cool in the darkroom with its little lights fogging everything in every direction. I got all of this for under $100 more!
You can use the dichroic color head as a continuous variable contrast filter on Ilford Multigrade paper...and the directions for the enlarger even break out the exact numbers for you. This is nice if you like to tweak your contrast and don't use single grade paper.
Now the bad rep these have gotten is due to the many ways you can adjust the lens board, neg stage, and head...(someone thought adding tilt to the lens board, for example, was a "feature") that are reputed to get out of alignment easily...within one printing session even. I have found that a good pocket level and a little care goes a long way to eliminating this problem. So far. I haven't printed any long runs so far, either...just a few at a time, and calibrate everything in the room before I begin.
The other problem can be the focussing mechanism...actually the head height adjustment, but usually called the focussing gear. In the early versions of this model, which was only made for about 5 years, a kind of plastic was used in the gearing mechanism as I understand it, and after a few years it disentegrated and gummed up the mechanism. You can buy a later model which solved this problem, or get an earlier model with the focus upgraded. You can sort of test this on a unit you are considering by grabbing the skinny knurled knob and just twisting it up and down, then grab the fatter knob, rotate it inward toward you, and try to lift and lower the head manually. If both moves are smooth and fairly effortless, its probably a great machine at this point...if they are very sluggish or don't release properly after a few tries, its more than a problem with lubrication.
The stand base is small for my work, and I haven't solved that exactly. I am not ready to remount it on a table top or wall, but I will get around to it. If you get the xl model it will do 16 x 20 prints on the base with up to a 90 mm enlarging lens and medium format film, and the head does rotate 90 degrees for wall projections.
So there are some things to watch for, but I have actually encountered others who own and use them, and are very happy with them. They are very well designed and made, as far as I am concerned...and the price was right.