I have a rusted up Sidekick.  I am going to strip it down sandblast the frame and start from there.  Are there after market tubs for it?  Any and all suggestions welcome on this build!

Not that I know of, there are enough clean tubs out there most people just get a new body or just weld in new body panels they make by hand.

What are you looking to do with the Sidekick?

Good after noon most of us that do rust repair just go to the local wrecking yard and cut parts off , where are you located ?

20-30 year old vehicles usually have some rust issues, but west side vehicles have very little rust compared to those eastern vehicles. 
Knowing where you are helps, so does photo's of what you are working on.  I have seen some really rusted out projects here restored, so you could get better answers with more information given.