This question has a pretty clear-cut answer - you should open a bank account for your venture as soon as possible. You can use your EIN number (which you can get online for any type of business, even if you are not incorporated) to open up a business banking account at any commercial bank. It is a good idea to do this sooner rather than later, because it can be difficult to look back and figure out what was, and was not, a business expense if everything is going through your personal account. This can make it hard to know how much you are earning (or spending) per month, how much personal capital you or others have contributed, and how the venture's finances look in general. If you choose a local credit union, you can likely open up a business banking account with No or Low monthly fees.