To do this, you need to have enough equity to qualify for a more traditional loan and there may be new loan origination costs and other factors to consider. 

Do not, do not, do not allowed someone who is not a licensed professional to install the furnace, it will invalidate the warranty.The warranty should be able the same from every manufacturer, so you're pretty much even there.I wouldn't necessarily recommend flex duct, it is cheaper, but you can end up with integrity issues, even in the short run.My best suggestion is to find an HVAC supplier, and check to see what the prices are for furnaces ... this will absolutely open your eyes as far as material costs are concerned.  

I'm factoring in PM as a "sunk cost" to all deals and want to cash flow even after that cost.  

There are many factors that play into this and not everyone is able to.

If you don't think I could qualify for a loan under my current circumstances, let me hear it.I want to contact a mortgage broker to get preapproved for a loan but I don't know if my earned income, as well as other factors would allow me to qualify.

I assume those factors drive price.

Is that based on an appraisal with your improvements factored in?

Based on economic and demographic factors alone, there are much better markets.

I'd say the #1 factor in how successful you'll be with them is who you buy through, i.e. the team.

@Lin-Chuan Lee in my rehab #s I included all inspections, legal & oops factor, etc.