Please know the experts in the second-hand SLR market to help me answer it.

Your classmate definitely doesn't like 50D after graduation. There will be something better then. Maybe 70 D and 80 D will come out. You can refer to the price of Canon's mid-range SLR two years ago, or even lower. Actually, you've already entered n, so why jump to C? I met a nice orange D200 the other day, only about 4500. In addition, the fuselage is updated too fast, and getting a few good heads is the right way.