If they used poison then you might be out of luck and have to wait as this means it could be anywhere, including most likely an inaccessible area.

If the area is inaccessible then you have to think what value your time has.

If that is the case, then yes, I would compensate them for the excessive disruption, based on the percentage of the home that was unusable/inaccessible.

Bathtubs must be inaccessible to children, meaning bathrooms with bathtubs would have to be locked.  

I think that a judge will say that you accepted the repair by the act of closing (unless the invoice misrepresented the work done).HVAC is one of the most expensive and technically inaccessible aspects of your property. 

Even if his opinion is overstated, it's hard to beat that kind of value appreciation in today's markets:  equities are overvalued, interest rates ensure fixed income investments don't yield much, and alternatives remain inaccessible to most investors due to investment minimums and securities law requirements like accreditation.What's more, there has been a flurry of development throughout the Boston area, including in my neighborhood. 

Need some experts to chime in. Access

They've been there for 5 years, that's all I know.So I have potential long term tenants in one of the units already, but its the unit I would be living in (access to basement, garage, etc.), So I'd either ask them to move into Unit 2, or ask them to vacate the property and have the tenants I have lined up move into Unit 2.  

Regardless of the cash flow you can get in Schenectady, I just can't stomach the lack of liquidity, it feels like putting money into a 401k that you just have to assume is inaccessible for the next 20+ years.  

I read it like you're building from scratch, in which case, you absolutely need to build in accessibility but you could check with the local jurisdiction to see if just having 1st floor accessibility is adequate or if you need accommodations for wheelchairs to make it up to the 2nd floor as well.