my professor recommended me to get a Canon 5D but is to expensive for only a class. Do you guys know of any other canon DSLR that has the same resolution but is more affordable?

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There are a number of DSLR that will fit your need for a class From Nikon the D60 is a good bit cheaper and while not the same resolution as a Canon 5D it will do all you need for the class. another great option may be to find a gently used D200. Unless you are doing very large prints a D40 may even do all you need, As important as the camera body will be good lenses. Particualrly a good wide angle lens for architural.

In this case the DSLR brand is not as important as the lens. Both Nikon and Canon have PC (perspective control) lenses which are designed for shooting using small format cameras and keeping the perspective of the building correct. Many professional architectural photographers still use view cameras with wide angle lenses and bag bellows when they are doing serious work for a client. When it comes to architectural photography, affordable was never in the cards If you are willing to correct the perspective in the camera (before you shoot) the Nikon D200 with a 12-24 mm lens will do the job ($800 for a good used body and just over $900 for the lens) and of course a good, sturdy tripod and leveling tool PC lens for Nikon 24 mm ... $1900 PC lens for Canon 28 mm Schneider ... $2050

I would think a view camera would be the way to go for architecture.