Thanks for the questions.
Yes, you can sign up today if you are taking the test in, say, a month. And I will contact you a week before your scheduled exam to say that you have two weeks to take our CAT (one before test and one week after).
No one will get paid without producing a score report from the actual GMAT.
We can mail people a check. There will be no "refund" as we are not affiliated with the actual GMAT. Though, yes, it is a nice way to get paid to study for the exam.
For those who take our test after taking the actual GMAT (and yes we want you folks too), we want to make sure you are incentivized -- so if your score on our tests is not within 120 points of your actual score you will not get paid.
Hopefully helpful,
Josh