My husband has hundreds of baseball, basketball, & football cards. What is the best way to find the value of these. Most are between 20 & 30 years old.

Was at my family’s house for the holiday weekend, was going though some old stuff and came across tons of baseball and football cards I used to collect back in the day. I have some complete baseball sets from back in 88-89-90, Fleer, Topps and Upper Deck. They were in surprisingly good condition.

Would something like this have value to somebody 18-20 years later?

While cleaning out an old closet, I came across a box full of old baseball, hockey and football cards. What is the best way to find out if they are worth anything?