If he is more involved or engages in the activity with regularity it would be treated accordingly as self employment Which could be a good thing from a tax planning standpoint.

Troop levels at the base change on a fairly regular basis. 

I'll be sure to post regularly on my REI adventures!

So in the case of me purchasing a property outright, even if I'm licensed, wouldn't I have the fiduciary duty to myself as the buyer, much like an buyer's agent would to their client in a regular real estate transaction?

If you have a regular buyers agent then ask them to look over it and figure out a way to compensate them. 

The spiral round duct cost double the cost of in-wall duct, but that is more than made up for in savings for creating soffits to house regular duct.  

However, the tenant is responsible for the cost to install, and remove those items when they leave.

If a regular refinance is say 4.125, a purchase or cash-out refinance will be about 4.25 or 4.325.

It regularly gets state inspections since it has some state occupants and he does not have his car dealer license.

She stopped paying rent, regularly this year, threatened to move out etc.