I'm currently at Willowbrook, and I absolutely love it. Management team is phenomenal, maintenance is pretty timely, and it's by far the cheapest apartments I've found for a 4bedroom place. I've lives at Avenue South as well, more expensive, but you get a private bathroom and the office staff there are also extremely nice and helpful. I have vet friends that are living at Baywater, Copper Beech, Riverwalk, that have all reported good experiences. Purdue Research Foundation has properties that are directly on campus and reasonably priced. A good friend of mine that is at Mizzou lived at Cottages on Lindberg. I've heard mixed things about Weida, Collegiate Communities, Peppermill (and other Hunter Lafayette proprietaries), Cole Property Management, KCB Management, W.H. Long, and probably a few others that I can't think of off the top of my head.
Whatever you do, do NOT rent an apartment from Granite. They by far have a huge monopoly on properties in West Lafayette and Lafayette and therefore have really cheap options, but have been known for shady practices upon moving out such as charging tenants excessive fees for carpet cleaning, painting, general apartment cleaning to the point where people have filed suits against the company.
You can look for a good swatch of properties on boilerapartments.com and local craigslist.
I'm currently in the search for apartments so I have a spreadsheet and more bookmarks than I can count lol