Contractor Charge for Scope of Work?

[Aleph Kennedy]

Hello Everyone!
I'm very close to actively looking for a distressed property to purchase, but before I start calling general contractors I want to know how to handle acquiring a scope of work from them? 

I plan to get a scope of work breakdown from 3 general contractors before moving forward. Am I expected to pay for them? If so how much? Or its the norm to for them submit the scope of work with the optimism of getting the contract for the rehab?

Your feedback will be greatly appreciated!