You asked
Best used full frame camera under 1000?
Here is what the site says about that.
From Buying used: Buying used: Cameras and lenses are built to last, and many photographers upgrade often. That makes the used market one of the best ways to afford good gear. A body that's one or two generations old is often most of the camera for a fraction of the price.
From Samyang AF 35mm f/2.8 FE: Samyang AF 35mm f/2.8 FE: A prime lens by Samyang for Full frame cameras, 35mm f/2.8. A pancake that weighs under 90 grams: the smallest 35mm for Sony full frame. It's on my camera most days.
Quoted from this site's pages.