Verweis : joshua_chanceOh & Can I just walk into a bank and ask for foreign coins and bank notes?
Here in the UK banks only deal in notes and there is no guarrantee as to the quality of the notes, they may be mint or they may be old and tatty.
Jewellers often sell gold and silver coins, not so much for coin collectors as for metal speculators (and there are a few of them using Numista!)
As for making money from coin dealing, I should assume that is the same as any other business, do your research, buy cheap and sell at a profit! To buy cheap you will need to exert effort seeking out coins, don't bother buying from dealers if you want to resell, rather look to private individuals, junk shops, car boot sales, garage sales, auctions and the like.
Personally I should avoid buying through e-bay, NEVER buy any coins you can not inspect first (unless you're buying bulk worthless foreign coins from a dealer of course).
Matt