I've got the feeling you're embarking on a project which involves a load bearing wall. If I may be so bold, unless you or the individual(s) doing the work know what they're doing, you'll find yourself sitting in your Home Owner Insurance Company's office explaining why the 2nd floor is now on the 1st floor.
Determining the load-walls is the relatively easy part. But what to do when you want to do work involving the load-walls is another. The contractor should be insured and bonded. Ask for proof, and get copies for your records. Here are a couple of links to help you with what you might have in mind.