Stamps.com - Buy Postage Online, Print USPS Stamps and Shipping Labels Trial account. They even give you free postage.
After you're FREE month is almost up, call them to cancel but tell them you're not too sure, and they'll give you another month free.
$30 on amazon for a scale and weight to calibrate, and you're good to print, and mail from home. or prep, and drop off at PO.
If you want to step it up again you could get a $100 Dymo label printer and it will print flat rate stamps adn other basics free, just labeler and label cost.
Anyway, I'm interested in 2 for testing and your old 1TB shoot me a PM when you decide if you're selling 1 by 1 or goign to try to sell ALL at once.