Like in Black/White 1&2 were certain people will by certain things from you and give you more money than the stores (ex: Maid @ Route 5 will buy berries/mushrooms/ect. from you for more than the stores).
http://www.serebii.net/xy/useful.shtml
According the Serebii and many other sites, there are no Maniacs to be found in the game so far. But maybe they're hidden and will be found on a later date.
