The problem with very inexpensive detectors is, they don't find much more than you can find with the naked eye. They can be very frustrating, and end up stuck in the closet and interest is lost in a very healthy and enjoyable hobby.
When asking what brand to buy, you are going to run into severe brand loyalty. For me, it is White's detectors. Their customer service is second to none, and they are outstanding to use. Pretty much all White's detectors come with presets so that you can get out and start detecting with good results right away with a minimum of manual reading, as well. For somebody just starting out, I tend to recommend finding a used White's Coinmaster Pro 5900 Di (with the blue control box) on Ebay or Craig's List. They can be had for as little as $175.00 and still work respectably well, even though they were made in the 80's. A Coinmaster 5900 or 6000 Di Pro series 3 is about as old as I would go, though.
These are my detectors, each has its special hunting environment or target. Not shown is my wife's White's M-6, a coin magnet if there ever was one and simple to use with one knob and one toggle switch!
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