Many seem to have extensive experience in creating value out of C class buildings.

What’s wrong with you People buying houses for 100k that require extensive work when the Arv is only 120 .

I only ask because I would like to buy one there at some point ;-)The extensive rehab (basically turned it into a brand new unit) was the bulk of the appreciation, followed by me getting in at a great price. 

If so, what should I do as far as an addendum or extension to the contract?  

And depending on how he deals with them (whether he tries to handle the claim himself, or hire a Public Adjuster, which I recommend), settlement amount can range drastically.Depending on the extensiveness of the damage, most of the time, Public Adjusters are looking out for the insured's best interest, since they work on a percentage of the proceeds, so they'll point things that need to be remedied to the insurance company, that the homeowner will have no clue about.

Forget getting so much as an extension on your mortgage contingency so get your lending in order and ready to close on time. 

Screen them extensively and be very selective.

I have been studying it extensively because I also plan to invest here this year.

I've been researching the market here pretty extensively over the last 6 months or so.

Ideally you offer 2 or 3 yrs depending on your circumstances with an option to have a one time 6 or 12 month extension.