@Jerzy You rang? 
For $500 or less you would be into a new RIA with a few bells and whistles.
Back to your original question though, you are looking on the used market for a 1911. What KIND of 1911 are you looking for? Something to approximate a 1911A1 military issue? Something with modern enhancements but still a 1911?
The next question, do you tinker with your firearms?
As to things to look for:
Frame to slide play: There will be “some” movement A lot is a bad thing.
Thumb safety: Make sure it works as designed.
Grip safety: with the thumb safety off you should not be able to send the hammer home without depressing the grip safety.
Trigger reset and sear safety check: Pull the rigger and hold it back, recock the hammer. The hammer should lock back and stay there. Now slowly let the trigger come forward. You will feel and possibly hear a “click” (less travel is better) at that point you should be able to pull the trigger again and have the hammer fall.
Firing pin check: If you brough a pencil with you point the gun straight up in the air and drop the pencil down the tube and let the hammer fall, the pencil should fly about 2.5 - 3’ up in the air. (this works for both series 70 and 80 pistols) Pushing on the firing pin from the back only works on series 70’s.
Chamber check: Lock the slide to the rear and LOOK into the chamber to see if it stock or if somebody has been inside the barrel or the ramp. Be familiar with what a stock ramp and barrel generally look like vs a modified one. If you see file marks or Dremel tracks hand it back. The barrel will move back and forth a bit, make sure when the barrel is pushed all the way back that it does not overhang the feed ramp, right up to the edge is fine.
I can’t believe I have to say this, look down the barrel and make sure there is a chamber and lands and grooves. After my son’s fiasco with a brand new Kimber I’ve added this to my bench checks.
Barrel & Bushing Check: With the slide locked back the barrel bushing should be snug in the slide. With the slide forward there should be no movement of the barrel in the bushing.
If they let you take the slide off do so and look for abuse to the frame rails and cracks over the slide release hole. If it has been used, there will be wear and but it should be the same on both sides.
The above will let you know if the gun has good bones but you will find out the truth on the range. Hope that helps
Cheers,
Craig6