First of all you need to define what does it mean 'bank' for you.Banking system is a very difficult and its not as easy as it seems,you need good  plan and another investors,employees,If i were in your place I would understand every institutional and financial regulations about it...
Its also important to define your financial activity in detail and create business plan,read more about norms promulgated by your country's national/federal bank.For example in my country if you want to create bank you must buy special licence which costs million dollar if not more.
But it sounds a bit antagonistic because as I know if you want to start this job you must create firm like joint-stock company or LLC how would it be decentralized when you will have legal duty to send your financial statistics and documents to the central bank, so I don't know maybe I'm wrong...