he is wanting to upgrade from his older gun why would he want to buy another used old gun
Because many "old" guns are in excellent shape (like new), cost considerably less than new, and shoot extremely well. Over half my rifles were gently used when I acquired them and I challenge anyone to tell which I acquired new or used on the basis of how they shoot or look.
Ruger M77, mfg 1989, acquired like new in 2004:
Remington M700 BDL. mfg 1975, acquired like new in 2005:
Ruger M77, mfg 1984, acquired in almost like new condition in 2006:
Recently I purchased a stainless/laminate Ruger MKII .30-06, in like new condition, and it has been shooting .5MOA consistently. Don’t have the manufacture date handy but I think it was 2002-2004, will have to check when I get home.
The point is there are a lot of high quality “used old guns” available and they can save the buyer hundreds of dollars – often enough to get a decent scope and still save the buyer money over the cost of a new rifle alone.