What is the best swan species to start out with?

I have mute swans, but I would like to have at least a pair of black swans some day.

All swans should have water at least a few feet deep because it is hard for them to support their weight on land for long periods of time.  This is particularly true of whooper swans.  Many states regulate the ownership of mute swans through the department of natural resources - I'm not sure about whooper swans.  Black swans are considered exotics because they are not native and do not fall under the migratory bird treaty act so they are not regulated  by the department of natural resources.  Black swans are also considered to be relatively docile.

I think whooper swans are not as available to buy as black swans.

     I personally would suggest the Black Swans.  I love their temperment. They are more tolerant of other fowl then many swans.They are easy to find and seem to be one of the least expensive of the swans. Mine are very curious and love to talk  to me. They seem to be more interactive with me than I have seen with other peoples swans. Mine dont care to be picked up, but they will let me. I have one who is handicapped and when he ventures too far and gets tired, I pick him and and he rides in the golf cart back to the mini pond. You can do a search on all my swan stories here.

I have 6 black swans, but I'm no expert....... but I do love them. They do need some type of water to swim in, but do seem to spend more time than most swans on land. Your feed store can order a swan diet and they spend a lot of time grazing grasses. Mine also like to raid the dog feeders... sigh, its hard to get the feeders somewhere those long necks don't reach... hehe.