I don't know the best places close to you for S/H gear, but it's not an expensive lens, nor is it rare, you should have no problem getting one locally - you definitely won't get one here though, there's almost no US activity on the classifieds - and postage would make any bargain lens expensive.
Beware also that there are four 'generations' of f-Mount Nikkor 50; I cant remember the exact designations; but you have the very early non AI coupled lenses; then the later 'coupled' versions; then came the body driven 'pin' actuation auto-focus lenses for the last Auto-Focus film cameras and early widgetals.. before you get to the relatively recent (2011) motor-in lens AF-S 50mm.
On the D3200, you don't have in camera AF motor, so the AF-S is the only one that will auto-focus on that body. The pin drive AF-G will still allow the camera to get aperture data from the lens and let you use in camera metering, but you will have to manually focus it. Previouse non AF lenses, wont talk to the camera's electrickery at all, and you will NOT be able to use any of the exposure modes but full manual, AND without the camera offering any metering info.
I use a legacy (Ziess) 50mm on adaptror on my D3200 fairly frequently; it's rather like using one of my fully manual old film cameras, and I have to either take light meter readings with a seperate hand held meter, or use another lens to get a meter reading from the camera, or simply 'chimp-it' taking test shots and adjusting settings by what they look like in preview.
I have used a pin drive AF 50 on it; It gave me meter data in the viewfinder and did work in 'program' as i recall, but had to be manually focused; so was akin to an old AI film SLR in use.
I ended up buying (For my daughter) the 50AF-S, that worked as it should on both my D3200 and her D3100. And it wasn't all that expensive, even brand new, after lots of disappointment trying to track one down 2nd hand, and finding most were pin-drive not AF-S.
So question really is how desperate you are for one, and why, and how much you'll likely use it.
If you are happy to tolerate a completely uncoupled 'legacy' lens, and metering with seperate meter or with another AFS lens as well as full manual settings and focus; then one of the early manual focus lenses may be acceptable; but likely also expensive, and a 3rd party lens like a Ziess and a mount adaptor may be cheaper and as 'good'
If you cant live without in camera metering, then the pindrive AF lenses do meter, but they wont be AF on your camera, and they are fairly common and usually quite cheap; and possibly as cheap as a legacy and mount.
Otherwise, you are probably going to struggle and as I had to, look at buying new.
But chucking teh googlie in to the mix; there is the matter that the 50, oft raved about for optics and it's 'standard' angle of view is legacy of when the 5 was the standard angle of lens and common prime fitted as 'kit' standard to 35mm film cameras, and basis of a lot of academic exercises. A 50mm lens on a crop sensor DSLR like the D3200 has the equivilent of a mild tele-photo, 75mm portrait lens on 35mm, and a 35mm lens the 'standard' angle of view of a 50 on 35mm film camera.
Nikon's AF-S 35, was introduced a few years before the 50mm version, due to people wanting 50's for the legacy reputation and finding them to be a different beast on a crop sensor camera; And if that is what you are hoping for, then the 35mm AF-S, may actually be your better bet; it's the 'standard' angle and fast prime for your crop sensor camera; all functions of the camera are enabled by it, so it all works as the kit lenses do, and it is the more common and possibly slightly more available 2nd hand; if the still relative bargain new price is still a bit steep. Both AF-S 35 and 50, are available for around the £150 mark here in the UK, and I believe retail in the US for under $200.