Hey guys, I just finished up my undergrad at WMU and I'm from the area originally.
There's a ton of housing around Kalamazoo, and most of it is pretty cheap. There are a ton of student apartments (because most Western students live off-campus), as well as plenty of apartments that aren't saturated with undergrads. There's a big residential area just south of campus that's mostly houses available for rent to students, and a lot of them are quite cheap (I lived in one of these for a couple of years, and paid $200 a month plus utilities with a couple of housemates). There are a number of apartments available in the area, and many of them are pretty reputable. As a grad student, I'd stay away from The Pointe and Copper Beech, because they're both full of undergrads and are usually the sites of loud parties at least three nights a week. If you're looking at renting a house, try to stay away from the north side--that's where Kalamazoo's serious crime tends to take place.
Otherwise, I really like the area. It's definitely not a huge city, but it has a lot of the college town amenities like cheap food and plenty of places with student discounts. Bell's Eccentric Cafe, the brewpub of Bell's, a well-respected microbrewery, is downtown and is a great place to hang out.
It's cold in the winter. The winter lasts a long time. It snowed yesterday, and I'm sure it won't be the last snow of the year. Being this close to Lake Michigan brings lake-effect snow and all that entails. The summer, however, is really nice.
Quick edit--the city is pretty pet-friendly as well. Quite a few apartments allow pets.
If anyone has any more questions, feel free to ask.