Walter built a burglar alarm company, National Security Systems in
Port Washington, New York, which both manufactured burglar alarm control panels and installed & serviced burglar alarm and access control systems in the
New York metropolitan area. Later, Walter began working with his family in
the Trump Organization, and was the executive vice president of Trump Management, Inc. During this time, Walter helped his family set up All County Building Supply and Maintenance, which he operated from the basement of his home at 511
Manhasset Woods Road; All County was founded in 1992. The Trumps used this company for the maintenance of a number of Trump-owned properties – including the Beach Haven apartment complex in Brooklyn. Walter and the four Trump children each owned a 20% stake in All County; Walter also received a portion of the markup for his work creating the invoices. In 1990,
Ivana Trump claimed in an interview that whenever Walter greeted Donald Trump in his Trump Organization office, he would click his heels together and say "
Heil Hitler," possibly as a
family joke. Walter was also the Trump family's historian, and managed much of the family's finances. Walter stored the family's financial records in his basement. In 2020, Walter was mentioned in
Mary L. Trump's book,
Too Much and Never Enough, as having helped his uncle,
Fred Trump, with
tax avoidance schemes. == Mayor of Flower Hill (1988–1996) ==