How do you go about determining market rate?

For underwriting purposes, adding 19,000 back to income for the purpose of determining DTI is very different than $1,000. its literally $19,000. 

I am seeking an investment minded real estate agent to work with me on determining (with substantiated estimates that I can share with my parents) the most advantageous path forward, which I believe would be 1) rehab and rent, 2) rehab and sell, or 3) sell “as is”.

Secondly, the property and strategy that's utilized will play a critical role in determining the best lending partner. 

Lenders look at creditworthiness/balance sheet/track record and the collateral in determining the leverage they will offer.

Quote from @Treza Edwards: What expenses are included in determining cash flow?

All disclosures are to the seller, escrow, IRS, that kind of thing.In one lawsuit, the judge determined that the lender had constructive notice because I had recorded the warranty deed and was making payments from my business checking account.

Determine a suitable market, type of home, and satisfactory set of financial conditions for your purchase.

Depending on a property by property basis you can determine if your wife has REPS or not, this determination will place the income in one or the other bucket. 

So what you'll want to pay attention to is the total upfront costs and how that impacts your interest rate - I'd encourage you if your lender hasn't already to do a break-even calculation to determine based on your hold and strategy how much costs yield you a positive ROI.