You can read about the differences here: Cost Segregation Study Approaches ExplainedLet’s first start with what the approaches:Detailed Engineering Approach from Actual Cost RecordsDetailed Engineering Cost Estimate ApproachSurvey or Letter ApproachResidual Estimation ApproachSampling or Modeling Approach"Rule of Thumb" ApproachSo which of these approaches is required by the IRS?

I have never held a mortgage 15 years (or even 12.5 years) and I have had quite a few mortgages.I claim that it is better to have the negative cash flow and use the $450k to achieve a return in excess of the 6%.  

So while I have family nearby I want to minimize excess wear and tear because 1.

Quote from @Shawn Questa: A few times I've reached out to Cash Buyers and they would tell me that they are a part of an Investment Group and that they are ready to quickly Close Deals would be happy to work with me.Later I would come to find out that they are actually a Group of Wholesalers, like me.I guess I would prefer to Work directly with the Investor, Cash Buyer or Flipper. 

. - The people that are monetized on actually closing deals are all saying this thing is highly implausible. 

I've been using Rat X and am convinced it doesn't actually kill them, currently just have snap traps in place.

Having rentals that just pay for themselves or generate excess cashflow you can tap for other things?

The people are a bit abrasive and the fees are excessive.

Ken, Actually both myself and my father-in-law have properties in Florida. 

Not only do they not repay funds, they claim we owe them additional funding for renovations that never actually happen.