It is recommended to use PayPal Goods and Services when paying for an item. There are no buyer protections when sending PayPal Friends and Family, Zelle, Google Pay, Venmo, CashApp, Crypto, among others.
Good luck finding $1's in mint condition. Most of them (including mine) look like they have been run through a blender. If I'm not mistaken @Smiff was on a mission a few years back trying to hunt down mint condition examples. The $5's on the other hand are obtainable, but would have to be cherry picked.