Evinrude V4's are good engines, for sure. But you're dealing with a 30-year old outboard, so check it out carefully. If you can see it run on a boat, that's best.
If not, at least try to stick it in a barrel and see how it idles in gear. Really hard to tell much about a motor that's run on the flusher. A large plastic water barrel works well for this.
Do a compression check if you can. Pull all the plugs, and crank over the engine with the kill switch lanyard pulled, so there will be no spark.
If you can't get a compression check done, wrap a rope around the flywheel and (with spark plugs installed & key off), pull it over smartly.
You should feel (4) solid compressions; if you have a "flat" cylinder you'll be able to tell. This certainly won't be the most accurate test, but in the absence of a compression gauge, better than nothing.
The engine should sound crisp, start right up, and idle well in gear (if you can test in the water).
Shouldn't knock or make other unpleasant noises. Should shift F/N/R without undo clunking/bad noises.
You should see a good stream of water from the telltale. Let it warm up, both heads should be warm but not uncomfortably hot.
If you can keep your hand on the head for a few seconds, it's no more than approx 140 deg F. If it's too hot to keep your hand on it, it's 180 deg F or more, and a good one to stay away from.
Check the gear oil in the lower unit by pulling the drain plug only. Oil should be clear, or maybe dark if it needs changing. But shouldn't be milky or milk-shake. Indicates water and a bad seal. Not an expensive repair if you can do it yourself.
Assume the motor will need an impeller, unless you know it's been recently changed.
The ideal situation would be if it's still on a boat and you can take it out for a test drive.
Failing that, if it's very clean, seems to have good compression, sounds good when running, it's probably worth a shot.
Check your local Craigslist ads for pricing comparisons, outboard pricing varies widely from region-to-region.
Don't give as much for a motor you can't check out thoroughly, and any issues you find can be used as a bargaining tool.