I'M STUCK!!! No idea how to estimate rehab cost

[Stephen Seaberry]

So I've read @J Scott's  The Book on Flipping Houses, purchased the Enterprise Edition of the house flipping spreadsheet, navigated Homewyse.com for hours, and I'm still stuck. I have absolutely no experience in construction and my DIY experience has been nothing more than putting up backsplash and painting in my home. I'm still learning terms like abatement and waterproofing. Today, I was doing a walk thru of a wholesale deal and could clearly see what needs to be done; the wholesaler even provided a proposal from a GC. Problem is, he's never used the GC, the GC provided a basic SOW with only a total costs, and I don't know how to estimate what those repairs should costs.

I have lengthy experience in preparing service contracts and analyzing costs, but in my 9-5 I rely on my customer to prepare the should-cost estimate which gives me a basis to determine if costs are reasonable. In this new world I've ventured into, I don't know where to start. Ideally, I would like to have 2 or 3 GC's meet me at the suspect property, walk thru taking notes on all repairs/upgrades needed, and within a few days provide a line item costs proposal. However, the few GCs I've reached out to show no interest in doing this. Is this normal, or should I keep looking until I find GCs that are willing to play? Bottom line, me trying to navigate Homewyse.com for every repair/upgrade needed will lead to me missing deals, so I need a more effective/efficient way to arrive at my rehab estimate. Can anyone provide any suggestions or advice for an ambitious newbie? Thanks in advance.