By looking at the yolk, a non-fertilized egg will have a small, white dot on the yolk, whereas a fertilized egg will have the same dot, but with a distinct, white ring around it - kind of like a bullseye. I can’t see a dot on the first yolk, but the second yolk looks to be unfertilized.
For candling, I find it’s best to candle between day 7 - 10 of incubation, but I’ve been able to see signs of life as early as day 4. You’ll want to candle from the fat end of the egg where the air cell is. If it’s non-fertilized / fertilized but not developing, the egg will appear to be yellow / orange the whole way through. If it’s fertilized and developing, you’ll be able to see red veins branching throughout the egg. The veins and embryo will slowly fill the egg, and eventually it’ll be too dark to see much of anything.
I can’t answer the selling / shipping eggs question, so sorry.