1992 Jeep Cherokee rear end

It could or could not be driveable due to what damage is done to it. If the gears are stripped off then it is not if it's bearings it cold be making a loud noise which insome case isi better to have it towed as well. Unless you talk to the person you really don't know what is wrong with it.

You're right; it can be a lot of different things. This is like saying, "it needs body work". A little more detail or explanation is necessary. If this is a locking differential, it could be chattering after a recent service. That can be the result of failing to add an additive with whale oil in it. That is not a serious problem but it can be an annoyance. A wheel bearing could be noisy. That can go on for years. Look at the pinion bearing and seal right behind where the drive shaft bolts on. If there's minor leakage, you replace the seal. If there's a mess including metal particles, there's enough chewed up that it's best to just get an entire assembly from the salvage yard. Check around first. The vehicle is old enough that finding an axle may be a problem.