Starting an online bank

What is involved in starting a bank? I am aware that rules might differ from country to country. But let's say I wanted to start an online bank in the US. What is needed?

In addition to Tim's answer, just be aware that: 1) You need a lot of money in liquid funds, since you have to put the funds in escrow accounts to guarantee solvency; 2) The rules are set by both the federal government and the individual states; and 3) You usually need to be a corporation, and the corporation usually needs to have multiple shareholders. These are broad terms because the rules vary by state, but suffice it to say, it's a big deal to start a bank.

You might be better off by starting a financial services (some states call them Money Services Business, or MSBs) company for what you want to do. For example if you were to do only money remittances (compete with Western Union), then you would focus only on that part of the rules that apply to you and the licensing is easier. Instead of having 800 pages of financial code that apply to your business, you would only have 100 pages :-).

Still it's difficult to do, but not as difficult as a bank.

What exactly is it you want to do? Look at Simple (http://simple.com/ ) as an example. They offer online banking and debits cards, all branded under their own name, but they're not the actual bank. They've partnered with a company called Bancorp, and it is they who hold the accounts. Perhaps that kind of arrangement would suit you.