Question about the book of rental property investing, please help

[Michael Nashed]

Hi 

this is Michael 38 years old, i am now reading the book of rental property investing by Brandon Turner and i read when he gives examples of buying the first rental property and the example was mainly about buying a fourplex property with 80K $ and taking 80% of it as a bank mortgage but through the example and explainations about numbers what confused me that the example calculating the net worth annually without taking the consideration of the monthly payment for the mortgage that should have been paid, so if any one can help and let me understand the calculation and if the monthly payment for the mortgage was included, i would be so appropriate it,

thanks in advance