How hard is it to find a teaching position at a community college with just a master's degree? Are they mostly hiring PHD's now?
Either really, but ideally something you can make a simple living on.
And if this is possible and one is interested in this route is anything in particular they should during their master's degree to prepare them and increase their chances of being hired?
Even at community colleges?
And, yeah, with adjuncting you don't really know how much money you'll be making, if any, in future semesters. People have compared it to migrant workers' situation in that respect. Not to mention that the full-time faculty have first dibs on the classes.
It's a nice way to have a supplemental income during grad school or if you have a full time job in the field (that's how adjuncting was originally supposed to be, people out in the "real world" who could teach and share their knowledge). But a lot of people adjunct for their only income and they're really struggling. Plus many adjuncts don't get benefits or retirement. My CC does have that, but our state college faculty also have a union.
Check out this article, for instance: http://www.npr.org/2013/09/22/224946206/adjunct-professor-dies-destitute-then-sparks-debate