i recently just bought a lifted jeep cherokee and i was wandering how you can telll if the under body was painted over.. the body looks good minor rust on the axles but i cannot tell if it was sray painted and if it was is that bad?

 

just going to have to look close or wait and see if it flakes off

 

like superj said, see if it flakes over. if you don't think it's sturdy, pull the carpet, and look for bubbling paint or obvious rust. i'm not sure if you're looking for a rust cover-up or just wondering what the original paint scheme is, but your paint code should be on your door tag.
usually you can tell if the vehicle has been painted over by the amount of orange peel in the paint. the factory bakes the paint on, but most shops will spray it and let it dry, creating more orange peel.
i wouldn't sand it to see what's under the paint, but if you absolutely must, it's the last resort. it's the worst way of finding out the original paint color. i would never sand to see the color.