Getting straight to the question. Say I want to run a cryptocurrency exchange platform where people could come and buy/sell Bitcoin or Altcoin. The way I understood I have to partner up with a Bank in Order to be able to buy coins and have them in my websites depository to sell and even be able to buy from people instantly in exchange for cash. What are the benefits of this? How much profit is in running such a website? Would be that much profit that could convince a Bank to invest in it?

And is there any way that I could run it with less deposit? like taking the money from user and the buy the Coin instantly and send it to them? like, being a middle man.