I knew two people who worked for RMI. One worked for three summers. One worked for 8 years doing miscelleneous guiding for other operations too.
Here is what I heard from them. Remember, this is what they told me. I never worked for RMI.
RMI likes college students. They are fit, have summers off, usually without any personal family commitments--it just fits well into their business model. They will hire teachers and other sorts of people including EMTs and other people who are not college students too.
RMI is a lot more political than what they thought it was going to be. Do not expect at all to make it to be a head/lead guide. The higher ups are there to stay and so there is no room for additional leadership.
Be clean cut and shaven. A lot of the clients are professionals.
If you are going to a tryout for RMI be knowledgeable about prussiks, ropes, knots, spacing on ropes, weather, glacial movement, crampons...etc. AND know how to explain all that stuff to people. If you are knowledgeable, but do not know how to teach newbies, then you will not get a job. In the teaching arena, remember, you have to do it over and over and over again.
Be in shape. In very good shape.