The Duplex in the back, (that's currently being used as storage) is 1400 sq ft. 

Understand what they want i.e apartments, self storage, or single tenant and go find it - simple concept vs. tying up a deal and dialing for dollars out of desperation.  

. -$100 will be charged/deducted from your security deposit if damaged or removed-cars must be registered and in operable condition. cars may not be used for storage. management reserves the right to tow any cars not in compliance-management will pay for drain clearance once per year. tenants are responsible for any other clogs. management reserves the right to deduct this from the security deposit-if the unit is part of HUD(section 8) and the unit fails inspection for sanitary reasons, management reserves the right to hire a professional cleaner and deduct $200 from the security deposit.

If they are uncooperative, it might take an attorney to file, and possibly you to pay for moving and storage of their personal items.  

The first one was a storage tank and then the water would flow into the actual heated tank. 

All contracts, options, or other devices not based upon a substantial consideration, or that are otherwise employed to permit an unlicensed person to sell, lease, or let real estate, the beneficial title to which has not, in good faith, passed to such party for a substantial consideration, are hereby declared void and ineffective in all cases, suits, or proceedings had or taken under this chapter; however, this section shall not apply to irrevocable gifts, to unconditional contracts to purchase, or to options based upon a substantial consideration actually paid and not subject to any agreements to return or right of return reserved.You will find cheerleaders promoting illegal actions.

Look for cities with low vacancy rates in storage.

All contracts, options, or other devices not based upon a substantial consideration, or that are otherwise employed to permit an unlicensed person to sell, lease, or let real estate, the beneficial title to which has not, in good faith, passed to such party for a substantial consideration, are hereby declared void and ineffective in all cases, suits, or proceedings had or taken under this chapter; however, this section shall not apply to irrevocable gifts, to unconditional contracts to purchase, or to options based upon a substantial consideration actually paid and not subject to any agreements to return or right of return reserved.Note it states they cannot advertise the property.

We also like mobile home parks and self storage plays with experienced operators.  

We've thought about self storage, 18 wheeler parking, or just selling it.