Usually I consider anything with bolt-on wheels not worth bothering with and the exceptions are incredibly few and far between. There are some entry level bike shop road bikes from the 80s that might make the cut. Anything department store may be worth salvaging tires/tubes but is usually scrap as is most any 70s bolt-on wheel bike. If it doesn't come with aluminum rims and a QR skewer it isn't worth taking a look at for me, I've got better things to do with my time.