Old town is charming. I lived in old town for the 1st 6 months of my masters program. while it is in walking distance to a lot of cool places, and the houses are charming, it also has its down sides:
1. Small, old houses at a high premium for their location
2. old houses have old issues- harder to heat, no AC, no dishwasher, small rooms, etc
3. Loud, annoying drunk people who throw trash in your yard, harass your dogs, and break your fence in drunken brawls (my experience). I have a service dog who was in training and after living in old town and a few bad experiences with passer-bys, she has become terrified and aggressive towards strange people. I also found Blue (I am guessing soaked in antifreeze) bread thrown in my yard.
So, old town does have its ups and downs. If I had LOTS of money there are some very lovely sections of old town, but on a vet school budget, I am guessing you will end up in a place more similar to my experience. The house was cute, but I would never live there again.
I cant really think of a bad area of Fort Collins. For me, I am not fond of living really close to train tracks or highways, so just look at the map (like on zillow) and you can see proximity of those things. Not sure how close you want to be to campus, but there are lots of newer homes north of Fort Collins at lower prices. Also, I know lots of people who live in wellington or Loveland and love it but it will give you like a 30 min commute. You will get a lot more house for your money, though.
But ya, I cannot stress how competitive the housing market is for renting or buying. March is a pretty good benchmark, if you wait until June/July it gets super insane. Start contacting companies, now to get your name on lists. Especially Kevco seems to have most of their properties pre-leased far in advance. Not all companies will keep a wait list, but some do. Be careful with craigslist. When I was looking, last year, I think 60-70% of the adds on there were scams.
http://northerncoloradorentals.com/ is a good site to use because people have to pay to list properties on it. also, when looking on craigslist make sure to look up the owner of record on the Larimer county assessors website and double check that is who you are working with. You can also type the address into Zillow.com and it will tell you if the home is in default or foreclosure. Since I spent the last 5 years working in real estate (primarily with foreclosure properties) there are two ways you can get into trouble with renting.
1) people will show you a foreclosed home and claim it is theirs, then they ask for your SSN and cash for credit check and you have essentially payed someone to steal your identity.
2) people will rent out their property and collect rent but they dont actually pay on it and the property goes into foreclosure, leaving the tenant with eviction notices and facing eviction by the bank (this is not a pleasant experience)
so be careful of those scenarios from craigslist rentals and check out the property before going ahead with it.