Multiple companies & other ?????

Lots of questions!!
First, pay rate and the amount for houseing stipend are going to vary by company and area of travel. Shope around companies to see what they are offering.
Most companies want you to have at least one year's experience in your specialty before traveling as you will need to hit the ground running when you get to the new hospital and will probably only have 1 week for orientation when you get there.
I know there are a lot of nurses who do work for more than one company, but I have not done this myself. However, I do have contacts with multiple companies so I can change if I want to for whatever reason.
Currently I am working for American Mobile on my first assignment (WOOT) and am planning on taking 2 weeks off to travel to my next assignment/stop off at home and make sure things are okay. With this company anyway, you can take off up to a month and still have benefits when you start the next assignment.
2 books I HIGHLY recommend (as someone who likes to do their homework before starting anything new) are Hitting the Road, by Shalon Kearney(EXCELLENT reference, well written!!) and Highway Hypodermics, by Epstein LaRue. I believe both are available on Amazon.com! They helped me a lot in my decision to take the leap and go after bigger adventures in life!!!!