Here is the funny story.
A couple of days ago I offered my quote to a buyer request. The job was making a digital drawing from a pencil sketch. It was a pretty easy job for me so I offered $10. The buyer responded the next day and wanted to place order. He requested me to send him another custom offer for $5 and said that he would tip $5. I agreed (though I never count on tip or ask any buyer for tip) and sent him revised offer, he placed order. Yesterday I delivered the finished work. after seeing he had no comment on the design, He just asked for an extra version (black/white). I delivered that too. Then he marked the order as complete and gave me a negative review.
And I’ve had the opportunity to get the taste of a negative review for the first time in my entire life.
Moral of the story:
Keep away from the buyer who negotiates tip before placing order.