I won't be going to CSU, and I haven't spent much time in Fort Collins, but my whole family is from Aspen, so I can give a teeny bit of help.
I will tell you that the closer you get to Aspen, the more dog friendly the places get. Also, it's pretty common to commute in Colorado (Aspen to Fort Collins is ridiculous, of course, but living in a different city is not unheard of).
Also, a LOT of people rent out rooms or "mother-in-law" suites in their houses, especially in the off seasons.
Again, some of this info may not be helpful, since I haven't spent a lot of time in Fort Collins, but I thought I'd give any info I had in hopes it might help someone.