how does cash flow increase BEFORE paying off loan?

[John LaMedica]

In the BP vid below, Brandon is analyzing a rental property for cash flow and says that his cash flow will go from an initial $1200 to $1500 by year five, then to $2000, then jumps to $9.5k once the loan is paid off. Can someone help me understand what causes the cash flow to increase BEFORE the loan is paid off? 

He did estimate that his income would increase by 1% per year, but that's only an extra ~$20/year, or an extra ~$80/year by year five, so that alone cannot account for the $300 increase in cash flow achieved (i.e. from $1200 to $1500), esp. since he estimated that his expenses would ALSO increase by 1% per year. 

 https://www.youtube.com/watch?v=hrOR9mYk0Vs&list=P...