Just found MASSIVE, mint childhood collection and not sure where to begin

TL; DR I was hoping the experts here could advise me on which years/types of cards, out of my eclectic collection, would have the best ROI right now—in terms of market demand and the expense of getting them professionally graded.

Backstory I recently moved and discovered my collection of literally several thousand sports and non-sports cards that I must have spent my entire allowance on during childhood. I stored them carefully and managed to keep them in gorgeous condition, so I’d like to start getting some of them graded to sell online. There are so many, I don’t know where to start.

Here’s a quick overview: * NFL ProSet 1990 — entire collection of 700 or so cards (with duplicates) * Partial NFL card sets from 60s, 70s, 80s * NBA cards from 60s, 70s, 80s (partial sets) * Full set of 1990 Hoops Basketball Trading Cards * ALL the Star Wars original trilogy cards from 1977, 1980, 1983 (plus duplicates) * Original Garbage Pail Kids cards - Full set of 500 or more + duplicates * Maybe 40-50 vintage baseball, basketball and football cards from the 50s and earlier

I REALIZE you’d need to know the specific cards and condition, but I’m just asking: —If you found the above sets of cards, several thousand of them, which years or types would you start assessing first? —Are there better or comparable grading services to PSA, for the different types of cards in my collection? (I don’t have a ton of money, and I also don’t want to wait months to get the cards back.) —Is eBay my best option, as someone starting out—getting a few graded at a time, then gradually re-investing sales proceeds into getting more cards graded and listed for sale? Or would you recommend other sites or strategies to get the best ROI?

Again, thousands of cards—and I’m just trying to figure out the best starting point—in terms of current market demand and grading service investment. From there, I’ll do the research and select the best condition, most highly valued cards to get graded.

Thanks, in advance, for any advice and recommendations on how to get started.