proprietary desks are sort of in-house hedge funds. in view of the large number of blowups in the recent years, some banks have disbanded many of those desks, they now basically focus on safe and cushy income like collecting commisions from clients.
any market making activity in spot currencies and vanilla derivatives is having a hard time right now because commisions are very low. there is some money in exotic derivatives because some clients are willing to pay big money for a custom structure.
but i know personally successful hedge funds out there that are making good profit trading currencies and currency derivatives.
as i said, nicholas, don't worry about the money right now worry about learning. go to the place that will give you the opportunity to learn the most. if you learn a lot about trading and about this business you will be fine.