A few years ago, garage sales produced an embarrassment of riches. For some reason these things seem to go in seasons around here. Five or six years ago it was Canon AE-1 season but the owners seemed to want excessive prices for them ($150 average) and I didn't bite. Then it was Minolta season and I bought XG-1, XM series, several SRT models, all for $5 to $10 with average lenses (the ubiquitous Minolta 45mm lens, sometimes a 50mm f/1.7 or f/2.) A large stack of film point n' shoots, never more than $1 each. Film cameras have fallen off in the last couple of years, though: we may have just about run through the stash of old film cameras. Now I mostly see older (2-3 mp) digitals. I gave most of that stuff away to kids who expressed an interest in photography; I think I have one XG-1 left from that time. My first darkroom was $25 from a garage sale; an anonymous "student" enlarger, a wooden crate full of trays, graduates, etc.
I was once offered a Leica. An elderly woman had a small sale in her garage; I glanced over it and said something innocuous to her. We got into a conversation and I mentioned an interest in photography. She had a Leica and some lenses; her deceased husband had brought them back from Europe after WWII. She offered them to me for $200, which at the time I actually had. But I couldn't do that to her. I gave her the name of a local fellow, who may or may not have given her a "fair" price but he gave her a lot more than $200 for it. I guess I'm just not a Leica guy.
Estate auctions are a more reliable source in my area. My very first very own 35mm camera was a Minolta SRT-101 with 58mm f/1.4 lens which I bought in the box at an estate auction for the princely sum of $44 or so. More recently, last spring I got a Nikon FE with the 55mm f/3.5 macro lens for $20 and an N2020 with the 35-70 zoom for $10, both at the same auction. I always wanted a macro lens but couldn't afford one in my youth; now that I mostly shoot 8x10 I have one! It's a lot of fun to play with, though: I have a couple of rolls I've shot at auctions where there wasn't anything of interest to me but I had to hang around because there were things my wife was interested in. I have some detail shots of some old toys, and in particular an old Coca-Cola sign, which I'm very excited about. I also have a whole gaggle of Yashica Electro 35 rangefinders (including two sets of the auxiliary lenses,) for $3-$5 each. I love those Electros; one of them came with the never-ready case and whichever one of them works has been my under-the-car-seat camera for years now, loaded with Tri-x.