I bought a $10 food scale at
WalMart several years back to weigh my packages. The scale works great. I just put my item in the box I'm shipping it in to ge the weight and put it into the postal calculator on my ebay auction. Simple.
I got my priority mail boxes free from ordering them on the postal website.
None of the post offices around here will give you boxes. They claim they don't have them.
You can put a postal calculator on your ebay auction so customers can put in their zipcode to see what postage is. You put in the package's weight, plus you can add handling fees to it if you wish. It's a lot better than guessing and hoping you didn't underestimate shipping costs. I've done that a lot having to pay extra shipping costs myself. After I bought my little $10 food scale it's been correct ever since.
Not all post offices will pick up your postage paid packages. Our post office won't. Our mail carrier doesn't walk. He drives from house to house with everyone having a mailbox out by the street. It wouldn't be that hard to pick up my prepaid packages, but nope. They would love for me to print out the labels myself, but I still have to drive to the post office, stand in line and then have them double check to be sure enough postage was paid. No more pre printing for me.
I also ALWAYS use delivery confirmation for EVERY package where a buyer paid with paypal. I add the delivery conf. cost onto my shipping price.
There are some shady buyers who will see you don't have the confirmation on your package and file for a refund with paypal.
If you have no valid delivery confirmation number then paypal will give your buyer a refund. It's not worth the risk, imho.
Ebay is fun most of the time. I wish you well in your selling.
