What to do/

Make a Discogs account. Add all the records with their condition. Put whole collection for sale.

Sell the whole collection to 1 buyer. You’ll be lucky to get 1$ each. Let the buyer sort them out. Most records aren’t worth much more than that wholesale. 

If you're located anywhere near the Chicago area there's a record store in Elk Grove Village called the Record Warehouse. 

A good friend and I sold the bulk of our collections there, and we were both shocked at what they offered us.

They specialize in rock and roll.

You will spend an ungodly amount of time selling them piecemeal.  That is your main consideration.

Most DJ’s are hard on records and equipment. Count the number of records and figure a dollar apiece for them and try to sell as one big lot. But don’t expect to get a thousand dollars for a thousand albums.
At a garage sale about six years ago, I bought roughly 975 CD’s for $150. I kept about a hundred to fill in voids in my collection and sold the 875 for a hundred dollars.

YRMV