I bought its AE1 brother for 10 dollars with the f1.4 lens, I'll give you the skinny
Check it to make sure it doesn't have the dreaded AE1/AT1 squeal, the shutter is on its way out if it does. It's a known issue. Dry fire it and if it squeals either on the fire or the film advance its going to be toast.
They take a 6v battery that looks like a tiny AAA
It's an orphan system, meaning no modern digital cameras can use its lenses. No new lenses are being made for it, which is good, FD glass is cheap. Many of the later lenses use the same optical formulas as their EOS counterparts, the 50 f1.4 is one of them as is the f1.8 version.
Check the light seals to see if they have been done, seal kits are 10 bucks on ebay if they haven't.
If it's like the AE1, the battery is required for the shutter to fire, it's a fully electronic shutter. There are no manual modes like on its Nikon counterpart where you can fire the shutter at 1/90th or Bulb without the battery, even Bulb mode needs the battery to operate. It does have a built in light-meter but it is manual exposure only, no shutter speed or aperture priority program settings. That's fine, some of the best cameras in the world were fully mechanical.
Be aware the shutter is a cloth shutter so don't touch it.
