I prefer my negotiation to take place long before a contractor hands me the bid.So, for me, it's pretty much take it or leave it...For example, my roofers have steadily raised their prices over the past 5 years (and lowered them a couple times). 

I've asked certain exterminators and roofers and they all have said they can't fix it.

The best way to avoid disasters in flipping is to locate and surround yourself with good professionals who know more than you do and listen to them before you leap into a property you can't walk away from easily.Before you go looking at properties,interview several contractors about their skills, education,and previous projects they have recently completed.Demand to see their licenses and insurance and verify absolutely everything they tell and show you.Demand references from previous clients and ask to see their completed work.Realize from the beginning that one guy can't and isn't gonna do it all.Most general contractors are carpenters and decoration specialists so you need to interview Plumbers,electricians,roofers,and foundation repair people too.Make sure they all know what your intentions are and that they on onboard with you asking for free inspections on a regular basis.

Even worked as a lead chaser for a roofer in Texas.

A good roofer can recommend if you shingle over or do a tear off. 

I am thinking as a roofer, instead of running after one-times leads, which is great, but I would rather have a long time working relationship and give them a good low price service, but its worth it if it is long term.

Problems to be solved: Roof: It most likely wasn't repaired correctly (Could be an easy fix, get a contractor or roofer in there to give you quotes) Does he have documentation for the repair of roof?

Then WCI has something like 10-13% on painter, plumber, electrician, other average at 15-20%, carpenter at 35-50% and roofer at 80-120%.

My strategy hiring roofer or any other sub contractor is buying my own material and just get a labor price.

My Boss (DAD) has done major jobs before which have turned out well, but not where I'm at right now.Flat Tar and Gravel Roofs:  Hard to find roofers who still do it and difficult to sell these properties.Recent Death in the Property:  This was a minor issue we suspect in a job that just got in escrow after a bit of a wait.