balls
I did a 757 rating recently (with a job guarantee at the end of it), but the TRTO also did self funded ratings. Everyone on my course has a job, as has most of the next course. There are 757 jobs around at the moment.
Go and have a look on ppjn.com and filter for 757, there are alot of operators around.
It is also a 767 rating and that is most definately not an 'obsolete type'.
Go for it, it is a lovely aircraft to fly.