I don't know cost details yet, and obviously that's a huge factor, but I was just curious if anyone here had given it a shot and how effective it was.

Those improvements are probably already factored into the price.Might make sense for owner-occupied considering you would not have another housing payment and or cash purchase which don't sound like a good fit for you at the moment.Nice job of coming to a decision based on good data instead of "ballparking it."

I use 55% to 60% expenses of SGI depending on factors that might cost me more in a fringe area.  

And always factor in active listings, sold listings, expired listings, and active/pending listings.

I would just mention the structural integrity of your flooring cannot exceed a weight capacity of 300lbs, any encumbrance above that is a safety hazard.

Factoring age in now, I'm wondering if two or three multifamily rentals over the next 3 to 5 years (trying to be realistic) will really get me that much closer to the financial independence I'm looking for out of real estate.

After you factor in HOA dues (if any), property management, vacancy, maintenance and capex, I think you may be lucky to net $20/month in cash flow.

Is anyone doing both purchasing/brokering discounted notes and factoring? 

From CBRE | 2016 Global Real Estate Market Outlook“Moderate economic growth with low interest rates, punctuated with bouts of pessimism and volatility—the factors that have characterized the world economy for the past few years—are likely to continue in 2016, supporting moderate growth in commercial rents and investment sales volume globally.”

You are forgetting to factor in basic repairs, capital expenditures, vacancy, etc..