Sterling plan to hire about 40 this year, they are not able to get that many for interviews at the moment. They might fire you if you fail the type rating course, if they dont need you when training is completed, or when your season contract has expired.
You might get hired with 600 SEP, but my friend have not been able to get an interview and he is type rated on the 737 (750 total SEP) . Sterling wants to make money on the type rating course, and they might train more people than they need to make some cash.
I think this is a poor deal, but go ahead if you can afford not to get hired after paying the type rating!!!