Cash buyers will be serious, not just wasting his time with offers, 30-45 day closing delay, inspections, appraisals. 

I ran the numbers on the deal knowing that I would break even on cash flow in the first year with minimal rent increases but significant cash flow in year 6 when the 401k loan is paid off.

Sounds like you got a property with minimal out of pocket.You could try posting the room on FB or Craigslist.

Fix-and-flip or builder’s risk insurance should be in place before work begins, and confirm your contractor obtains all necessary permits to avoid delays.

I apologize the the delayed response.

They can provide serious cash flow with minimal owner involvement.  

The taxes can make things difficult, but there are some things you can do to minimize their impact.  

minimizing free cash flow with larger mortgages or shorter term mortgages takes the cash flow which would be taxed and puts it into the amortization of the loan. 

I’m hoping to not build until I acquire more revenue from profits of the plot via flea market, parking, boat parking, or something else that requires minimal investment.

I see a lot of LL compare their old unit that hasn't been remodeled in 15 years and has delayed maintenance to some newer units.... they create a vacancy but jumping to what they see as market and that vacancy and remodel costs them tons of $$ that takes YEARS to catch up on with that jump to market.