Investigators said Thursday that 56-year-old Dwayne Young kept the man locked in a basement for four months while cashing his benefit checks.
Capt. Laurence Nodiff says Young threatened 63-year-old William Richardson into signing the checks.
Nodiff says police are investigating whether Young had committed similar acts before against his common-law wife, who died in March.
Police who raided Young's home on Sunday found Richardson locked in a basement.
Investigators say Young kidnapped Richardson in April near where he worked as a handyman in South Philadelphia.
Young was arraigned Wednesday and held on $1 million bail. Court records don't list an attorney for him.