The costs are significant, since the banking industry is the most regulated industry in the country. Banks generally need between $12 to $20 million in starting capital. If you start a local community bank, you might be able to raise that money locally. Otherwise, you may have to solicit investors. Once the capital is raised, you must apply to regulatory agencies. Regulators are strict in their review of applications since the financial crisis. Once you're approved, you may open up your bank.