Typically, to qualify for loans when contract or self employed, you need two years of tax returns for a typical loan.

Re rent roll, obtain copies of the executed leases and validate collection via bank statements and tax returns. 

The total of all depreciation taken is taxed.

@Dennis Hill if the house meets standards of that size family, enough beds baths and room size for children, then follow your standard rules, like I make anyone 18+ years of age qualify on their own unless they are a dependent of main tenant (prove with current tax return).

You can always complete a line of credit or cash out refinance and repurpose that equity while keeping the asset (all tax free money). 

Are there any creative strategies for them to secure the loan without it affecting my DTI? 

We are not married, but I charge her 'rent' which is a little less than 1/2 the mortgage.Are there any tax benefits to saying she's a renter and I'm the landlord?

Taxes are low in Philly.

But there are implications to that strategy so be sure to discuss your specific situation with qualified tax expert as this is not a tax advice and I’m not a tax expert. 

I highly recommend it.If you have any other questions or need any bookkeeping or tax help, please feel free to reach out.