Best older 35mm camera under $100?

Well I already have a digital set-up, I have a Nikon D7000 and a D3100 with Nikon lenses.
So I've been interested in 35mm photography lately. I know it's a more intimate experience with the camera, and you get to control everything about the photo, and I love that!
At the moment, I don't want to spend more than $100-120 on a camera with a lens. I was looking at the Pentax K1000, is that a good one? Any other good ones?

Look on craigslist in a city near you.

You really want to get a Nikon 35 mm so you can use your same lenses. Look for an N series camera like a N65, N70 or N80. All your Nikkor lenses will work with them, even the DX lenses although you will get some interesting vignetting

I'm with Ace on this one. Nothing wrong with the K1000 but it would be foolish to get a film body for another system if you are already into nikon. A decent N75 or even better, an N80 should be possible within your budget.

It's not exactly true that your existing lenses will work with a film SLR, as your current lenses are likely designed for the smaller sensor size of the D3100 and D7000.

That being said, you still should get a used Nikon film SLR, because any lenses you get for the film camera can be used on the D7000 (and probably manually focused on the D3100 unless you get AF-S lenses).

In checking eBay, it's easy to find used Nikon N80 bodies for $50 to $100, often with an included lens or lenses. The standard autofocus zoom for the N80 is the 28-80mm Nikkor, which is equivalent to the 18-55mm zoom lens of the D3100 kit.

Moving up the scale, there's the F100 which goes for about $200 used; moving down the scale there's the N65 and N75 which are about the same price as the N80 but not as well made. Personally, I own and use a Nikon N80, and that's the camera I would recommend.

Why not the Pentax K1000? It is an excellent and well-made camera, but here's some things you should know:
1) It's a manual focus camera, no autofocus.
2) You'd have to carry around lenses from a completely different system, incompatible with your current Nikons
3) It uses CdS metering cells, and if you don't put the lens cap back on, the batteries will drain.
4) No option for a motor winder

If you do want a manual focus camera, try a used Nikon FM10 or if you're lucky a used Nikon FM2. Very nice cameras, but you'll have to do some hard shopping to hit your price point.

The Pentax K1000 is the student camera. Extreme durable and cheap. It is also completely manual. When it come to film camera, you have a lot of choices

Canon AE-1
Olympus OM-1
Pentax MX or LX
Konica Minolta Maxxum 5
Nikon FM2

I have really just touched the surface. There are a lot of other great cameras out there. Definitely budget $50 or so to take the camera to Repair shop so they can properly service it. Most of these cameras are going to be 20+ years old.