In most cases, there are items that can be added back in, such as depreciation and amortization as well as a few others. But when it comes down to it, a positive income is rarely a bad sign. To do the math, divide the net income by 12 and you have the monthly payment the customer can afford. This is not absolute but it will get you in the ballpark. It is simply the current assets minus the current liabilities.
Current liabilities are due within one fiscal year.
The more current assets compared to the current liabilities the better the ability to service current debt and future debt. This is a tricky one. In a perfect world you would always have more net worth than you would ever have debt. But that rarely happens. The norm is for a company to be leveraged.