You will probably need to get a Sales Tax ID and certificate and file monthly, quarterly or annual Sales Tax Returns. How often you have to file will depend on the laws for your state and may depend on your gross sales. If you don't already have a separate Business Bank account, it's a good idea to get one. A separate bank account keeps everything straight for the IRS and other government agencies. You'll probably end up with several accounts for different purposes as your business grows.
Many banks have small business introductory offers.
These may include free checking for a limited time, business lines of credit and other useful items. Shop the banks in your area and compare their small business packages. You may find that the best bank for your personal account is not the best bank for your business account. You tested your code. Users do things that you as a developer would never dream of doing.