If you paint it (encapsulate it) and it's solid you should be ok.

I wouldn't take this on as DIY, but would pay for a pro to handle it either through encapsulation or abatement. 

You have 2 options:1) if it’s in decent condition, you can encapsulate.

So essentially you want to encapsulate whatever existing damage/mold/rot is present in the wall? 

It encapsulates the exterior and the best air sealing measures come from sealing the inside.

You definitely do not want to encapsulate the smell but eliminate it.

encapsulating the mattress is also good but that won't get rid of a place already infested.If it was clear who started it, then you could bill them with the rent, but you might have facilitated the spread by defering treatment and DIY treatment so you might no longer have any standing to bill that tenant for other units except maybe the treatment cost for that unit where it started originally. not sure...Good luck!

@Sabina HasanThe asbestos siding is not a problem unless you are drilling or cutting it (making it friable) ... it is also one of the easiest asbestos products to either abate (aka: remove) or encapsulate (cover with insulation and new siding ... though this does not remove the risk of exposure if holes are being drilled through the new and old siding.I'd be more concerned about the electrical and radon.  

A lot of people will incorrectly tell you that you can encapsulate the surfaces with paint.

Triple coating windowsills in a lead encapsulating paint... repainting "friction points" (think doorjambs, old cabinet doors, etc.)... repainting old wooden porches/decks... all of these things can reduce the potential lead hazard without breaking the bank.