GC says "You're a waste of my time"

[Phillip S.]

Needless to say I'm not having beginner's luck when it comes to connecting with a general contractor.  I have attempted to contact 3 different GCs thus far and only heard back from one.  The one that responded pretty much said "You're a waste of my time. I only work with experienced investors.  Contact me when you have a property under contract and then I'll come out and give an estimate for $300."   So let me get this straight.  I'm supposed to put a property under contract before I even know what the construction costs are going to be for the rehab?  Is there something I'm doing wrong here?