I sort of accidentally stumbled into collecting, but as a previous film user, I just got more interested in rangefinders, more specifically, the cheaper Japanese RF's. Since then, I've added a few different types, including some SLR,s, but not just limited to 35mm. I've got a couple of Fuji GSW690III's, a Pentax 645 with 75, 45 and 120 macro lens (and an adapter for my digital Canon - I hope that's not a dirty word around here!), a couple of 110's, inc Pentax and Minolta, and a few 35mm's as well. Canon QL17GIII (Black), Konica Auto S3, s2 and s1, Ricoh Super Shot, Minolta 11. and about 10 Yashica's, everything from an MG, Electro to GTN and Lymx 14IC. Not all work but most do, and depending on how I feel, I'll just grab one and put a roll through it. I just love using them. As to my guidelines, if I want it and can afford it, I will. I haven't gone anywhere near Leica's and the like yet (I've got an XPan though), but I probably will sometime soon.