I lived in a small town in WA and heard a sad story from the guy who owned the gas station in town - he was required to upgrade the underground tanks and it cost him an arm and a leg. 

IN CA OR WA  same thing if your bidding on a first then 99% of the issues go away .

I live in Rockville, MD and invest in Montgonety, Frederick, Prince Georges Counties as well as DC

Reston Virginia, the first master-planned community in the United States founded in 1964, is a Garden City about 20 miles outside of Downtown Washington D.C., which was recently added to the Washington D.C.

While you don't need a license in MD, you do need a PM, brokers or associate brokers license in DC to manage property....and depending on where in MD the properties are, you might by nessecity need to include DC as a practical matter.

City officials are pointing fingers at landlords, suggesting they're charging inflated rents to maximize the voucher payout.Mayor Whitmire reportedly lobbied for more funding in Washington back in May. 

Again in CA folks coming in from Vietnam war would go out into the mountains of the state and federal forests and basically kill anything that moved and ate them..was  a real issue about wiped out the black bear population and in Wa. my brother in law worked for the road department and would find dogs that had been eaten it happens..

Some counties in Virginia loves them because they have little employment so no big population increase = more burden on schools and the tax basis is very high because of the personal property inside of them so they pay a lot in taxesAs you mention need to be near a power source and I spent 5 years trying to get one approved in 30 acre parcel that the county wanted the site for something else - so they can be challengingTo get zoning approved they are really perfectly suited for Rural WA and OR along the Columbia River with all the hydro right there.. and they have built some over the last 20 years..

@Yul Shin@Dominic CourtneyIn the events tab of Biggerpockets, there is a list of meetups and REIA's throughout the DC metro area. 

I'm sure there are differences between AZ and WA, but the approach is the same.