maintenance company; management company
A company that manages or maintains buildings, facilities, or properties. Often used for apartment building management, facility maintenance, or property management firms.
The management company for this apartment building is responsible for cleaning the common areas.
I asked the maintenance company to repair the air conditioner.
proprietary company
Business term for a company that holds and manages assets, intellectual property, or subsidiaries, often without direct operational involvement. Less common in everyday conversation.
The corporate group established a proprietary company specializing in asset management.