Section 121 question

[John Hua]

Hi all, 

Me and my wife live in our SFH full time for the past year. In the upcoming year, we are getting roommates to help with expenses while continuing occupying as primary residence. We have ~400k in gains after improvements. My questions is how does section 121 apply in our situation(married couple)?

-If we sell after year 2, do we claim 250k(yr 1) and 125k(yr 2 with half the house rented) for total deduction of 325k gain? 

-What happens if we continue to rent out half the house, does at some point we get to claim the full 500k deduction? 

or is it calculated differently entirely?

Thanks in advanced!

John