Beginning in the 1970s, Gary Jennison Sr. co-founded CMJ Management Company LLC, Corcoran Jennison Management LLC, Westminster Company LLC, and most recently Gary Sr. co-founded Jennison Management Company LLC (JMC) in 2017 with his sons Gary Jennison Jr. and Greg Jennison as a second-generation real estate management company that manages all properties owned by JE Properties LLC. JMC, CMJ Management Company LLC, Corcoran Jennison Management LLC, Westminster Company LLC have collectively been responsible for the management of over 15,000 units of Section 8, LIHTC, mixed-income, and market rate apartments, as well as over 500,000 SF of commercial real estate in 19 different states.

Gary Jennison Sr. remains active in the oversight of JMC and has served on various Industry Boards, and he is also recognized as a HUD-approved Large Borrower.

In 2010, Gary Jennison Jr. was named President of CMJ Management Company and Westminster Company LLC, and since 2017 now also serves as President of JMC. Since 2010, Gary Jr. has deployed over $100 million of capital reinvestment into the properties, implemented extensive social service programs for residents, upgraded numerous facilities and systems to provide better accommodations. Gary Jennison Jr. also serves on the Board of Directors of the National Housing & Rehabilitation Association, local civic associations and is a CPA.

JMC self-manages its entire real estate portfolio with properties located in Florida, South Carolina, and Virginia. The JMC team oversees day to day asset management activities and is responsible for implementing consistent policies and programs throughout its portfolio.