Would it be a good idea to put in mobile homes (assuming that we could get approval from the township), put in storage spaces that could be rented out or to build additional rental/condo units? 

You can diversify within real estate itself, be it acting as a private lender, purchasing notes, investing in a fund, buying a storage facility, etc. 

there are brokers who specialize in selling these google themalthough I have looked at it and owned parks that had both.one thing to keep in mind and this is state specific  though is RVs are much tougher on sewer systems with all the chemicals that go into their sewage tanks. 

Two septic tanks on property & one water well.

And tell them you will dispose of it afterwards;  you are not a storage company. 

There is a 38-unit self storage facility listed on MLS with average rent of $60/unit; Built in 1998; located in Porter, TX, which is in Montgomery County (north of Houston).

I personally do it in the self storage sector and own multiple properties 800-1000 miles away. 

Two septic tanks on property & one water well.

Kevin O'Leary (from Shark Tank) was one of the speakers. 

What if market tanks and property is not worth that much?