Is it worth paying a structural engineer to assess to be able to develop a scope and cost estimate, and if the number work out it's do-able?

Zillow tends to be a large protractor in terms of its ability to give reasonable estimates of home values.

Purchase price and estimated costs and cash flow and goals I'm assuming would be handy info, but what kind of layout?

I will show you why its a deal, with real comps, I will show you how I do repair estimates, I'll let you know what marketing I did to find the deal, I will show you what I expect to make from you when you buy for cash, etc.  

Scott The Book on Flipping Houses, The Book on Estimating ReHab Costs http://www.biggerpockets.com/flippingbookDownload BP’s newest book here some good due diligence in Chapter 10.

If you want them I would get quotes from others in the area and compare that to your 7000 dollar estimate form your builder.

Also have no experience in construction and therefore lack the confidence to make an estimate on those costs when evaluating properties. 

The estimate value of that house is around $650K.

Also, I need to get someone in there to estimate the extent of the termite damage.  

What will be an estimated market value of a property over the term yo hold it?