QuickBooks is reasonably priced and extremely mature. It does what it does for reasons that you may not realize now, but you'll be extremely happy that it does them after a few months, like, the first time you need to file corporate income taxes, or the first time you get audited for payroll withholding.
If your only customer is the Apple App Store, well, you have one customer. You certainly have vendors. Anything you buy for the business is bought from a vendor.
If you're paying salaries, you have to calculate payroll taxes (and then pay them). This is pretty complicated. Even the biggest companies outsource it to companies like ADP or PayChex, who don't do a very good job. Intuit's payroll service, built into QuickBooks, will do a great job of calculating payroll taxes, withholding them, filing them with the government, etc. Don't try to play that game where your employees are "1099 contractors." You WILL get audited for this (we did).
You can try to roll your own accounting software, if your time is worth $0.00001/hour, or you can just do what almost every other small business does... use QuickBooks, learn how to do basic bookkeeping, and hire an accountant to check in and make sure you're doing everything right. Tax evasion is a pretty stupid problem to have, especially if it's not intentional!