Buying eggs IMO is a gamble....you never know what you;ve got until its YOURS. Call around to the local feed stores....there may be someone thats got a fresh hatch. Some even hatch a few themselves for sale. I know around here they stopped all shipments for several months because it was too hot but they started shipping again in Sept/Oct and I'm sure live birds are available. You can take day old birds no problem as long as you provide the heat, feed, water and some attention. They even swim at 1st day....just keep an eye on them...they can;t float well until they get feathers and they can drown when their down/fur gets soaked and weighs them down.They also get tired easily when swimming. First month you have to stay with them and only use shallow water for swim time. (2-3" deep) A daily swim in the sink helps keep the crusty-butt away and allows them to exercise. besides, they love it and are too much fun to watch. Mine all enjoy the shower massage....like a duck jaquzzi.
Avg is $3 to $15 like others have said, for good quality common breed duck eggs. But, My last bird was $5 at several weeks of age. That was Oct.
As far as sexing....physical sexing should be done the first day BEFORE the bird eats. Much easier without poo in the way.....
Do some googling. You-Tube also has some stuff on ducks. There are videos and detailed instructions. Its not as bad as it looks...just be gentle. If you're unsure, then don;t.
If you never saw the "Dirty Jobs" episode about a duck farm....the several people that did the sexing of thousands of birds each day sat at a long table and grabbed day old hatchlings out of big boxes and took a look, then TOSSED them into the appropiate box labeled Male or Female. All of a ducks (M&F) parts that every animal has are all contained inside whats called the "vent". The vent is a multi-purpose pouch or opening where all the organs hide. This is to keep the ducks underside as streamlined as possible so they are like a boat hull in the water. Very efficient and smooth when swimming. You have to gently squeeze around the vent as if trying to pop a pimple and the organs will come out (if male) or not, if female. But, its easy to hurt the baby if done too harshly. On a day old duckling its challanging just being able to SEE the vent...much less the microscopic organs hidden inside.
The ducks not too excited about this either...
A little traumatic for their first experience with humans but they get over it. Bug (my little girl) to this day still hates being held that way....(bottom up or on her back)
The only other way of sexing is to wait....for sounds, females are much louder and chatter more. The coloring is next. See whats typical for your breed. There are clues on the beak as well...beak color, the tip and its shape. Sometimes the legs have different color on M-F. If you don;t sex the bird the first week, you have to wait. The older the bird gets the harder it is to sex one physically. And messy too...Like nasty silly string...
BTW....tossing the ducklings in a box does'nt hurt them,....There is an old saying " ducklings don't break, they bounce". Thats true. I've never tossed a duck but I've had ducklings walk off tables, jump out of boxes and THUD on the floor...and they just get up and waddle away.