Add a neutral wire?

Can I add a neutral wire? I am replacing my light switches and outlets with smart ones. I had the basement redone a few years ago, and replacing those was easy because the wiring was correct. However, in the main part of the house, none of the switches have neutral wires (and one doesn't have a ground wire). I asked my regular electrician about it and he said I would have to rewire the whole house and then repair the drywall. Can I fish a neutral wire down to the switches and join it to the neutral wire in the junctions in the attic? I am willing to do the work if I have the info. Thanks.

 

A neutral conductor is required to be with the ungrounded (hot) conductors in a cable or conduit. You cannot just run a single wire separately. If your house is wired in conduit (flex or EMT) you can likely pull in a neutral wire. If it is run with cable, then you would have to abandon the cable and run a new one.

As a side note: This is why the latest code requires a neutral in every box.