Ari,
Probabaly best you past, but if it is a folding stock, and an Itilain reproduction, they are quite nice and as pointed out, if in almost new shape, worth about $200. I had a used one I sold last year for $150.00. The stocks that we are referring to are exact replicas of the WWII USGI version. NO plastic on those. If the one you were looking at had black plastic body to it, that sounds more like a Choate stock or the new Kahr folder (by Choate I believe). They fold to the side and the main body is plastic. Never liked the looks of those.
Yes, Universals can be problematic, you have to know what to look for. I would not buy what I call a "Flat Op Rod" version. That is in the later stages when Universal had changed the recoil system to a dual guide and spring model. You can't readily pull one apart at a gun store to see it, but if you know where the single GI style guide rod and recoil spring are located, and you DON'T see one there, then it is more than likely the dual rod style. Avoid the Flat Op Rod Universals at all costs, unless they are giving you the gun. Known to have cracking issues and reliability issues.
NOW, to add exception to the rule, if you find a carbine and it says "Universal" and it has what looks like a GI slide on it, then those are actually quite good. I still wouldn't pay over $500, but then you were talking about a gun with a $200 stock, so if you deduct that, they were looking for about 300 for the gun. If it was GI style Op rod, I would grab it! I have owned a number of those early Universals and they have all proved to be reliable rifles. Even more so than some Iver Johnsons and Plainfields I have owned.
Today's market, you can probably get a good Universal (GI Op Rod) for under $400. No folding stock, bit then again, MAYBE?
Wouldn't pay over $450 for an Iver Johnson or Plainfield, unless it is one of the stainless steel versions.
Both IJ and Big P made "paratrooper" collapsing stocks for their carbines. Don't let people get crazy with you on those either. Saw a stainless rifle with collapsing stock got for $650 recently and that was probably about right. Blued version should be about $550 or even less if the gun or stock are well used. Word of warning, where the wire stock collapses, at the rear of the main body, the wooden channels that house the wire stock are notorious for cracking. You will find almost all of them have some degree of cracking, from invisible hairline, to chunks missing.
Yeah, except for the 9mm dedicated version as mentioned, there has not been any .22 conversions that I am aware of. Seems to me Ceiner is missing the boat there, as they make a Mini 14 .22 conversion, so not much of a stretch to imagine they could make one for the M1 carbine. With ammo like it is, I think the time is ripe.
Good Luck!