I've sold to 0 feedback buyers. Even had one close the account before giving feedback, but they had received their item and I had the money, so I didn't stress and no bad came of it. Always use PayPal, always ship tracked, always open communication(if they seem like scammers or bots, no deal), always take lots of photos(tagged and dated), always cover your ass.
If you haven't sold a lot of items and gotten plenty of feedback, they'll hold your money for ~21 days. If you print your own labels, PayPal will unfreeze whatever amount you paid for shipping. After the item is marked delivered, your money should be available in a few days, although I've only found this with smaller sales, I had to wait the full 21 days after selling a card for ~$300 despite sending it 2-day.