Estate sales, unorganized ones, are usually a good place to find all kinds of valuable things for resale and profit. Kids are just in a big rush to sell the house so they really don't care...just want it all gone. You can take your profit and add to your chosen stack with it.
I used/still have an Ebay account but stopped buying and selling in the mid '90s Do a little research on precious and semi precious stones...they can be had pretty cheap and they look real cool in a clear bowl on the coffee table. People pick them up and all of a sudden want a few. Pretty much sell themselves.
The 18K ruby ring is long gone...so is a very fine tiny 22K horse I got...I was told it was valued at over 5 grand because of the fine jewels and workmanship with the reins, saddle and stirrups. I was happy with 3 grand. I got it for 10 bucks.
Also if you can, buy stamp collections if they're cheap. Research your Ebay.
Keep on Steem'n on!