$500 - $550 or so, for a basic model in good condition. Firearms hold up their value pretty well.
20-200 uSD
20-100
20-30 USD
No
A Glock 20 (third generation) will retail for about $600 in good condition.
100-10000 USD
20-60 or so
5-200
$20-$50
20-50 USD
20-60 usd
20-80 usd