Brevard County Sheriff's Major Andrew Walters said the man went to the home in Cape Canaveral on Thursday. That's when he found the remains inside a car in the garage.
Walters said it's unclear how long the body had been there, or how the person died. An autopsy is underway.
The body is believed to be that of a woman. Investigators think it may the home's previous owner, because she hasn't been seen for a while. She went through foreclosure earlier this year.
Mortgage lender Wells Fargo sold the home Wednesday. Neighbors told authorities that the woman had "disappeared" some time ago.