One of my tenants has asked if they could put a storage unit outside behind their space since they are out of space.

'We are not packing his stuff up and moving it to a storage unit. 

You can discover this by networking with active investors who engage in buy and hold (this can contain multifamily, office, retail, self storage, manufactured housing communities, single family, etc.), buy renovate and flip, note investing, hard money lending, WHATEVER. 

I have always rented my properties out during deployments, putting your stuff in a storage facility with BAH and rent rolling in is a smarter option.Step 3: when you return home, you can choose to move back into your property or buy that fixer upper you have been dreaming of depending on how much longer you have before your next PCS.

I am trying to put an offer together for a self storage facility that is currently 79% physical and 70% economically occupied.

But if your buy a 2/1 & 2/1.5 fourplex for $300,000, the value is likely in the $80-90/ft2, so it likely will not support new construction, if this is the case, the lots are more of a liability, although there may be other uses (putting storage sheds on them and renting storage space for your tenants, parking etc.)

Any in-ground tanks (active or inactive)2.

I would contact a professional to see what your options are before you tank your credit.

Now nationally, things could be about to tank again, but I haven't been watching so much.  

You might want to consider shifting some of your portfolio into asset classes such as self storage, medical office or multifamily just to name a few.