The stuff you can't sell online, you could sell from your garage on the weekends. Many neighborhoods plan annual or bi-annual yard sales. If you have items to sell, this is a great time to do it as the neighborhood as a whole can bring in a lot of traffic and help you perform better than you would on your own. If that's not possible, consider partnering up with a couple of families in a popular neighborhood.
Another site worth checking out is BookScouter, which will check the selling price on 55 different vendors. The list will include the offer price, how they pay (Paypal, check, etc.) as well as whether they pay for shipping and under what terms. If you have a lot of books to sell, they can search up to 3000 ISBNs in a single request if you upgrade to BookScouter Pro. There is also historical prices too in case you want to review trends.
How much will you make? I think my best month with Google AdSense was almost $5,000 over the last ten years. That amazing month blew my mind since it was actually near the beginning of my blogging journey. When you go from making zero to $5,000 in a month, that will rock your world. For me, it also got me even more excited because I knew there were other ways to monetize.