If those extra payments are going to move the numbers below your minimum investment criteria, then no, it is a poor way of funding a down payment.

Unless you can charge a premium on rent for having hardwoods that is enough to offset the extra cost of install, perhaps consider vinyl or laminate? 

I am self-employed, and even though I have a sparkly credit rating and plenty of savings to make the cut, meeting the underwriters' requests turned into an extra part-time job for several weeks.

(which I don't think she is) It would also add a ton of extra closing costs that wouldn't have been involved when whole-selling.

You're not required to do anything extra.  

Remember with commercial units / loans there will be a lot of extra fees involved: two closings, maybe two appraisals ($1600 for a 5 unit that I did recently), permits, inspections etc.  

It's really a math equation here Deb, but we're missing a piece of the info, and that is what you can reasonably expect to gain in rent from having the extra bedroom.

You get a significant rent bump with the extra bedroom.  

I'm not sure what their split is.Starting out you'll have to be extra cautious since you may not know how this contractor performs.

And to tell you the truth, the low price sets off a few red flags to me.