If you are looking for established retailers or auction houses with a strong track record of buying collections, consider these options: Midtown Comics
Selling to a local comic book shop is often the fastest way to turn a collection into cash. While stores typically offer less than what you might get selling to another collector directly—often around 30% to 50% of the book's retail value—they provide immediate payment and handle the logistics of resale. Where to Sell Your Comics comic book shops that buy comics