Buying a used tire to carry as a spare?

I bought my class A and was fortunate to have a full spare (with what appears to be a great rim) as well as an unmounted Spare and an extra rim. I haven't thoroughly looked them over, but they look decent. At least good enough to get to a shop to get a new tire on.

Like others have said, you're only limited to what You can lift by yourself really. No guarantee anyone will come along and help you out the tire on, and in an emergency that can be bad. But so is blowing a tire haha.