Gilligan,
Here are some generalized strategies you might find useful.
First focus on properties that are distressed (brownfields for example). What you want is a property that has some environmental liability that you can use to devalue the property and negotiate a better purchase price. The contamination must be fairly limited and any remediation can be achieved through encapsulation and bioremediation (aka natural attenuation). Avoid properties contaminated with heavy metals (lead, arsenic etc) and asbestos since these will not attenuate in-situ. The advantage to self storage in this scenario is that only one or two people will be working at the site in an administrative setting (no exposure to the contamination since the whole property will be paved - no pathway), so EPA and state equivalents are more willing to negotiate a natural attenuation remediation solution. Other then the initial evaluation, there is no cost as opposed to mechanical or chemical remediation, but you can use the remediation costs as a negotation tool during the purchase (don't let the seller know you intentions). Use a reliable environmental consultant - don't try and make these decisions yourself. Depending on your state, you may be able to recoup all of the environmental consulting costs and get some excellent tax breaks by redeveloping a brownfield property.
The second factor is geographic location relative to future growth. Look at conceptual plans of the department of transportation, hospitals, airports, universities, shopping malls, etc. Your looking for property that some large governement or quasi-government agency will have to purchase in order to accomodate future growth. Future highway ramps are great for this. You want something that is just outside restrictive urban develoopment codes. Since the property will be generating income, it helps to protect/compensate you from eminent domain.
Now you have a property that has the right zoning and can sit for twenty years generating an income while you depreciate the structures (which require minimal maintenance as you mentioned). A piece of property that is already fully developed and can be redeveloped inexpensively (low demo costs) is very attractive to future buyers because they will often be able to avoid the restrictive development codes (open space requirements, stormwater etc...) that come hand in hand with building in areas of urban sprawl.
