How to set up a payment gateway
gm: Coming from a financial services guy:  Look at the legal aspects first before you sit down and write code.  It sounds like you are jumping right into the transfer money aspect of it, bypassing the laws ytou need to comply with.If you are in the middle of a money transactions you are subject to many federal and state laws, and if you deal with international, you are subject to more federal and state laws, as well as those of the country you are transferring to.You will be imprisoned if you do not.  Since Sept 11 everyone involved takes these things extremely seriously, they will jail you first, and investigate later. (not to mention close your company and impound all your equipment).EDIT:  And you will need much more than your gut estimate of $1.5 mill because there are huge bonds to be put in _per_state_ you want to do business in.  Money transmission is not a business for the small guy any more.EDIT2: Have a sip of the legal requirements http://www.fincen.gov/ (this is just for the federal government, each state has its own office that places additional restrictions on you as well)