I did a brief search on KEH. The lenses don't look to be too bad. I would start out with a 50mm and MAYBE eventually get a short tele and a wide, but those both run on the order of $100 each. Doesn't seem too unreasonable. Perhaps you are referring to some other systems that are a lot cheaper? I am open to suggestions. I don't know much about the M42 mount but a brief look at the Pentax Spotmatic shows me it's about the same pricewise. Also, the FM2n is quite expensive (relatively) and the lenses look to be comparable. That's a more expensive option overall, and I'm looking for something relatively cheap. I'm doing this to mess around and have fun and shoot film and able to take quality pictures with a 35mm "sensor," but the body has to be around $100 or less.
Get OM-1n and OM-2n. A good CLA for OM-1n will last for next 10-20 years and other things to consider are the lenses. Certainly they are not cheap.
I personally recommend cameras with M42 mount.
If you have enough case then think about Nikon FM2n or FM3a.