Tenant may be running a business

[Yengkong Sayaovong]

On the contract, it states tenant may not run a business on property. Tenant is an auto mechanic. He claims he's not running a business and just helping out friends but downstairs says that multiple cars comes by during the day for past 2 months for him to fix their cars. Downstairs neighbor has complained that his business is disturbing her. He fixes cars until well over midnight and making noises. How can you tell if it's a business or just him helping friends?