I'm in the process of buying a house and the lower level is an
unfinished basement. There is NM cable drooping unsupported
under the joists to single bulb light fixtures. Naturally I want
to get this fixed as soon as possible. I've been told to just
staple the wire to the bottom of the joists, but I believe this
violates NEC 334.15(C). Even if it didn't, it would look awful
and possibly cause problems someday when I finish the basement.

So the solution is to drill holes in the joists and rewire.
However, there is a hot air duct (uninsulated) that runs parallel
to and between the joists that the wiring has to cross.

How should this be handled? Does NM cable have to protected from
the potentially hot duct? Should it be run in a conduit? How
should I route the cable around the duct?

Thanks
-T