So if the original contract does not mention an inspection period, you'll have to accept it as written unless an amendment is signed. 

Clearly I want their things out of the house but it appears they are trying to hold me hostage and use the property for storage for an indefinite period of time.

Since we will not have the time to actively pursue real estate investments  during this period, what are tips on staying engaged in the market and ready to roll once he returns home?

I typically use a 15 Business day inspection period and "This Contract is contingent upon Buyer's partners' inspection and approval at the sole discretion of Buyer's partners any time before the inspection period ends.

I've just stumbled across this concept of a "Seasoning period". 

Some of the regulations hope to create better management by making the owners be present during the rental periods (I.e.multifamily, cottage house, guest house, MIL suite, etc).

Period.

There is a hold period required to capture the full benefits of the OZ. 

If your engagement is for a year-round advisory, then he should be expecting your periodic need for his time and plan accordingly.Since you mentioned that his firm was specializing in tax planning, and you have discussed your needs, it seems like your requests should not have been unexpected for your CPA.

And unless you're a contractor, or very experienced in rehabbing properties, I'd recommend hiring an inspector to go through the property while you're under contract and in your inspection period.