Reusing clapboard siding

Thus far, if you are the homowner you only have to worry about your own conscience and health. 

Not sure on the reselling issue-re. homowner v. contractor.

My first inclination would be to suggest you  try removing b/4 making any big plans on whether any of it will be reusable.  Alot will depend on the nails used originally and any used since.  Further, if nailed into oak or other local framing used that will not let those nails come out.

A few yrs ago-maybe 4, I remove the siding from one side of a barn beam type framed house that was c. 1870 or so.   Cut nails originally, all sorts of add ons later.  The beams purlins and knee braces it was nailed to was predominately oak, the siding poplar-not beveled-pretty much 5/8" thick, edge to edge.

The cut nails would usually stay fastened, the siding pulled off over the 'head'.  Leaves a rather large hole-these were face nailed.   Some of the other nails, not so easy to remove w/o damaging the siding.  Some ring shanks were used, those damn ardox that would NOT come up period.........the heads would only break off when using a prybar, catspaw, claw hammer.........anything.  If you got under it, there was no prying against anything other than siding.........end result-splits breaks and toothpicks.

But, if you can, I'd use the good stuff on the shed, you won't have enough extra to sell I don't think. 

The siding I took off had several non lead coats over it-there wasn't much "falling off" that RRP practices wouldn't catch.