Sorry to hear about your business closing down, dude. It's never easy to let go of something you've worked on for so long. As for your tax papers, it's generally recommended to keep them for at least seven years. That should cover you in case of any audits or legal stuff. Yeah, I know it's a pain to deal with paperwork, but it's better to be safe, ya know?
Selling the materials and machinery sounds like a solid plan. You could check out scrap yards in your area to see if they're interested. It might be a hassle, but hey, every little bit helps, right? If you're looking to promote the sale, you could consider using a guest posting service. They can help you get the word out and reach a wider audience.