There are a few good books you can read on Construction Cost, one is "The Book on Estimating Rehab Cost" by J Scott.Doing additions to convert a two family to a one family really does not make sense.

Otherwise my offer will be “X” because I’m going to have to spend “X” to pay someone to turn it back.Then tell them that a 1/1 in their area goes for “X” and that is where your offer came from.Just use “kid gloves” because it’s possible that some sort of disability (i.e. going up/down stairs) led them to chose that location.Good advice and makes sense, but in my area (and other sellers' markets with low inventory) that could cost you the deal on a listed property.

That should help insure some sense of priority and trust to find the right "investment." 

Before I started learning about RE, I did a streamline refinance on 237k with a fixed 3.25%, at the time it did make sense.

Lets say you have a 100 year old house that is not in a super great shape, would not it makes sense to sell it when market is up and buy something newer?

Others apply a little more common sense to the equation in addition to the analytics.  

I think this is why internal rate of return exists - I know we're talking about rules of thumb, but if I've got a property in an area expecting lots of rent growth, I can add value in other ways, etc. over the course of a few years, the present value of those future cash flows and any other liquidity events become very important and it could make sense to accept a much lower CoC in the near term. 

Was your 290 number just trying to hit a home run, or is that where the numbers actually make sense?

I guess considering how I have a COC return of 16% it might make more sense to just do the cash out refi and try and snowball from there.

It might make sense to evaluate that as well as any potential for a value-add and refi on one of them.