Is rental income applied to social security earnings?

[James Fisher]

I feel like I should know this already, but am drawing a blank.

As an example:

John is 35 and has worked for 20 years.  He has enough 'good' years to draw social security when he hits 65 (or whatever).   Also, John has rentals that generates $75,000 (net) per year.  He decides it is time to quit his day job, and live off of his rental income.

Since social security at age 65 (just an example) is based off of his 30 best years, once John quits his day job do years 21 to 30 count as 0?  Or does the income generated from his rental income get applied?