I sold over 30 items last year. Every piece was in mint condition as evidenced by the photos I posted in the add. As I had previously posted as to the why ( a hearing issue suddenly appeared after my 76th birthday that is un-treatable), no explanation was needed. Every buyer was a Head-fier and familiar to me thru many conversations here and in PM's over several years.. All were in the US but one who was north of the boarder. I decided I would not sell to any other locales than US and Canada. I had 2 buyers who took several pieces that drove to me to pick them up in person.
Keep in mind not only the sale price but shipping and insurance costs and PayPal fees as well, especially if it is a piece of electronics. Do you or the customer want a signature at delivery? People used to go with the friends and family pay method for no fee but I think all that has changed and it may still be re-portable.
Have a PayPal account to receive payments. I would then have PayPal transfer it to my bank account, I let them do it slow boat way for no additional fees. There is a fee for every sale received, I think it was around 3% in 2022.
Keep a close tracking of what you sold, to who, address and phone number and e-mail. for how much and the costs involved. (I have a folder as thick as a Sears catalogue of documentation of sales / purchases going back to Jan 2016 when I returned to the hobby in earnest. Mostly e-mail receipts and listings of purchases with companies like Schiit has) and the buyers info. It's also all backed up to a USB drive.) There may be a starting limit of $600.00 or something, for reporting, but rules change all the time and are dictated by IRS.
You also need to have documentation to backup the fact that you sold for less than you paid in the event of audit so no capital gain.
As you are not actually a business you can't write-off any loss.
There is a form (can't remember which one now) that goes with your tax return, if audited (unlikely) and PayPal is required to issue a 1099 for received payments.
Your buyer can initiate the sale payment to your PayPal account or you can have an invoice sent by PayPal to the buyer.
Certified bank checks and legitimate money orders may be okay but the "Know Your Customer " rule is in full force and effect. If your selling something the buyer is your "customer".
With 40 years in banking before retiring I knew of 2 money transfers of substantial amounts that got reversed and the recipients lost their money.
My biggest sale was was a certified check from someone I knew well. There was no 1099 involved but I reported it anyway because I was able to document my costs recovered were about 50% and wanted to see if it triggered anything so I could dance into the IRS office and sing "Na,Na,Na Na Naaaaaaaaaaaaaaaa!" I made my my last 2 sales in early 2023, I'll report them and that will be the end of it.
I didn't realize how much moola I had invested until I started selling the stuff, and it was beaucoup bucks. I felt fortunate to have recouped around 50% plus or minus some shipping and insurance costs. When ever possible I'd throw in some extras (accessories (but not Herbie's LOL), tubes, CD's, hp stands, etc., stuff I foresaw no future use for.
Side Bar: I do like using PayPal to pay sellers, rather than have my credit card numbers and other info floating around in a hack-able database with perhaps dozens of selling entities. And no fee (yet) to use it to pay others.
There is a post somewhere on this website that speaks to how to use the classifieds. I believe the info above is accurate but subject to correction,
and Good luck!