Depends on how many eggs you want and how much room you have and how much chicken poop you want to deal with! I have 8 girls under one year that are laying, and I have been getting about 6 eggs per day. Now that the days are shorter, they are not so consistent. Only 4 today and yesterday. One girl went broody for a while and didn't lay for about 3 weeks.
After they turn 2 years, the egg production will slow down quite a bit. Also consider that some breeds are much more productive layers than others.
As for ducks, they are cute as can be, but are messier and a bit more work providing a dunking pool. There are some breeds that are good egg layers. They can be compatible with chickens, but know that if a drake mates with a chicken, he can kill her (incompatible anatomy).
I have 5 Salmon Faverolles and 2 Dorking's. For some reason there on a laying spree. I have been getting 7 to 9 eggs a day(more than normal because some lay in the middl of night an I can't collect until 5 pm every day) this has been going on for 3 weeks. I feel bad because they haven't taken a break. I'm also planing on getting 3-5 more chickens, each a different type.
I can say, the more chickens/poultry, the more food they will eat. My roosters were the worst. I also find I have to clean the straw under the roosts every few days.
There really fun, it really depends what all you want.
Some people who have a lot of birds will sell eggs. I have 5 hens. 3 greats layers and 2 so so layers. With only 2 people in my family we end up with lots of extras but not really enough to sell. I give them away to friends, neighbors and family from time to time. I also feed raw eggs to my dogs. Very healthy treat if you have dogs - mine even eat the shell.