Contracts that are signed are legally binding in most cases. They should not be signed until you are very sure of what you are signing and what is included and what it not. Also you should know about where you sre going to be working, what the facility is like, what the area is like, etc.
before you sign on the dotted line. Questions should be asked and answered before you sign, not after you have signed.
And many of these contracts now have cancellation clauses that go into effect as soon as you sign. Even before they start any paperwork for you, or you even take an exam if they are paying for it. And many that I have seen are for $8,000 US minimum once you have signed. And if you cancel, you are legally bound to pay that fee to them.
So please, take the time to do your homework, same as you would if you were purchasing a car or even a home. Get everything answered before you sign the purchase agreement. This is not any different.
And if it sounds too good to be true, it probably is. Remember that many of the recruiters/agencies that are overseas have never even been to the US and know nothing about how we do things in the US. Take the time to do some searches on your own before doing anything else.
Contracts--please read before signing one
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On the spot signing and telling you you can't take a copy of the contract home first for review are one of the red flags and take the time to go to diff. agencies first so that you have more options. Not that some agencies will be much diff. or you won't run into some problems w/ them but it would be much better that you made a choice from agencies 1-7 rather than just agencies 1 and 2. 
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