So how do you start. I would love a cypress. Just find a seedling 4" tall. Put in pot. Water daily and trim
You can do that. I'd wire the trunk in an "S" shape.
Bonsai simply means tree in a pot. It can be any variety as long as it has small foilage. I'd recommend getting a book that teaches the basic styling techniques. For a bald cypress, you can start out planting cypress balls. It will take decades to look as impressive as those pics posted by wick.
If you keep it in a deep pot, it won't look like a traditional bonsai, but at least it will live. Shallow pots can dry out in a day in the summertime. These are outdoor trees and most varieties need full or partial sun.