Another contractor's opinion - Please don't call a contractor and use their "free home estimates" without the intention of using them. It costs us alot of money to walk off a paying job site, spend gas to get to you, and spend the hour or two that a good contractor will take to thoroughly go through your project with you - especially if we are a mom-n-pop operation offering free estimates to struggling home owners.
Also remember that contractors have special contact boards just like BP - and we do talk amongst ourselves. It might not be such a big deal in a huge city, but in a place like Boise, it will get you black listed very quickly. Those of us in the construction trade are pretty close knit and we try to help each other, even though we may be competing for the same work. We need each other in case someone lands a huge contract and needs to "borrow" workers from another rival company just to get the job done. If you are identified as a time waster, you will be labeled as such and your construction rates just went up by quite a bit should you actually choose to hire someone after wasting a bunch of contractor's time.
HOWEVER, most of us DO like to help real estate investors and homeowners! For a fair fee, we'll be glad to spend the hour or two, walk through the project, and explain why certain things may be a problem and what you need to look for. We encourage you to ask questions, take notes, and call us in the future if something else comes up. Most good contractors will be happy to spend the time to teach you about hidden landmines that most people don't see until it's too late. Not only will you gain valuable knowledge to help you with your investment endeavors, you will gain a positive reputation in the construction community and people will more than likely be agreeable to offer you discounts and such.
Just my two cents. :-)