how I can get my foot in the door to work in student affairs?
First of all, you will need to know if the school you are interested in working at their student affairs department, is
offering any post for employment and what their offers is
Secondly, about obtaining an additional degree, such as the masters you talked about, its a good idea. Now you will need to plan well, for your self, either working first, then obtaining the Masters later or Obtain the masters and then seeking the job. if you choose to go for the masters first, then you will earn higher pay, as compare to working first and obtaining the Masters later.
There are many school offering a master program in Communication Studies, all you need to do is check that which is available in your locality or online.