Congrats to your friend on the vet program acceptance!
Unfortunately your disappointment about the housing market here is realistic. Housing is extremely scarce in Fort Collins, but on the bright side pet-friendly rentals more common in Colorado than in other parts of the country. Many private and management-company rentals accept dogs with an additional deposit, but six dogs and a cat will be a very hard sell nevertheless.
Horse properties on the outskirts of town or in neighboring, more rural towns occasionally come up for rent, but tend to be more house than a student needs and therefore more pricey than just renting an apartment in town and boarding a horse or two, especially when you factor in feed/hay/bedding/labor. You are more likely to find a 2-3 bedroom house with a field/no shelter/no riding facilities than a decent barn with a tiny house. For four horses (and a lot of other critters) it may be worth looking for a horse property rental, in spite of high rent and commute time, but I can’t imagine affording such a thing as a student. Once she’s here it might be possible to find a private rental that includes space for a horse, but those situations are often arranged through connections or advertised only by word of mouth, and tend to involve some shared space with the property owners that might again be prohibitive with that many dogs.
A lot of the student-oriented rentals have leases that start in August, and get shown/rented several months in advance of the move-in date (i.e. starting now). Other apartments also tend to get listed/shown well before they are available. In other words, securing housing well in advance is a good strategy in this town, especially for a move in that coincides with the academic year. Craigslist should give you a fair representation of what is available. It is probably also worth reaching out to the vet school to see if they have ways of networking incoming students with students who are already here and have a finger on the pulse of the animal-friendly rental market.
The horse community depends a bit on what end of the equestrian world you come from. There are lots of folks in both English and western disciplines here and a good number of back yard horses, but the horse community as a whole seems less tightly networked than in other regions I’ve lived in. With an equine studies program and vet school at CSU there may be a better-defined horse community within the student body that I’m not aware of.
There are lots of inexpensive boarding options in and around town, but none that I’d consider bargains. The average quality of care here leaves a lot to be desired in my book, though if you are used to rougher board and don’t need an arena with good footing you might find things close in that will satisfy you at a reasonable cost. Availability tends to be inversely correlated with care and facilities (e.g. places with indoor arenas tend to have fewer openings, especially as you head into fall and winter). Even the pricier barns tend to require some compromises, but it’s always hard to adjust to boarding when you’re used to having the care just how you like it.
I hope your friend finds some gems in the rental/boarding scene here and enjoys her time at CSU.