never done it, so needed to know if there are any questions/concerns I should have...
things running in my head are:
how do I know they are fertile eggs? You're going to pretty much have to take the word of the seller for this one. There isn't really any way to tell if an egg is fertile before putting it in the incubator, so you just have to have faith that at least some of them will be and will develop. You can always ask the seller what their fertility rate has been with their own eggs at home and/or what kind of hatch rate others have had with their eggs. Just remember, not everyone is going to get the same hatch rate with shipped eggs even if they were shipped the same distance and from the same pen because one day you might get someone who is extra rough with the packages they're handling and the next you might have someone who handles them appropriately at the post office.
how do I know that they will be "good" to incubate after shipping? Again, this is kind of a leap of faith thing here. Shipping is rough on eggs and there's no guarantee that any eggs you have shipped will survive the handling in transit. Things like broken eggs are easy to spot, but detached air cells and hairline cracks are not immediately obvious. Sometimes you can catch these things with candling, sometimes not. There are some excellent subjects here on how to increase your odds with hatched eggs.
lets say they ship same day or day after they are laid..and it takes 3 or so days to get to me...??? they'll still be viable once in incubator??They should be fine. Fresh eggs are easier to incubate, but eggs can be a lot older than many people think and still be viable. I am working on my first hatch right now. It was not planned, but we lost our rooster suddenly and did not have time to plan on collecting hatching eggs and just kind of threw everything we had into the incubator. The oldest eggs were easily a week and a half old. We're on day 11 and so far the only eggs that don't have live and moving embryos in them are the ones that were not fertile to begin with and were all tossed by day 5. Some of the girls were not fans of our rooster, and we had never actually seen him mount any of the hens so it was not a surprise that 49% of the eggs were not fertile. I have heard of people having successful hatches with eggs as old as a month.