A friend lives in Portland, ME. There is a house behind his that he'd like to buy, but cannot locate who owns it.

The elderly woman who owned it had a reverse mortgage. She died. Her son inherited it and he died 6 months after her. Her sister said the reverse mortgage company went out of business. 

Someone checks on the house, pays taxes, pays for upkeep, etc. 

Public Records show the elderly lady still owns the house. 

He asked the guy who mows the lawn, who pays him. The guy said a government agency, but declined to name the agency.

Anyone in Portland who can help me solve this mystery?