How is "Income" Defined in Debt-to-Income (DTI) Ratio?

[Manson C.]

A family member of mine is looking to get a Fannie Freddie loan for an investment property. He had a stable job in the same industry for the previous 20 years, but was unemployed for the past 18 months. About a month ago he got a new job in the same industry again.

I was told that in order to qualify for Fannie Freddie loan, DTI ratio needs to be under 45%. The question is: How is income counted for him?

Scenario #1: 

If you look at the income from his new job's paystub for the past month x 12, his DTI will be under 45%. Hence - Qualified.

Scenario #2: 

If you look at his last year's W2 or his year-to-date income, his income has been zero until he started his new job a month ago. DTI will be above 45%. Hence - Not qualified.

Scenario #3: 

If you look at his employment history before he was unemployed, he was having stable income for 20 years. DTI was under 45%. Hence - Qualified.

Which scenario is true when lender calculates DTI ratio?

Thanks.