The River City Company will help the county try to figure out what to do with its former high-rise jail at 601 Walnut St.
All prisoners were earlier moved to the Silverdale facility.
Grand juries for many years had called for the discontinued use of the downtown jail, citing many deficiencies.
Both County Mayor Jim Coppinger and Emily Mack of the River City Company said the building "has many challenges."
One option to be studied is its demolition.
River City will not charge the county for the project.
The jail was opened in 1976 and initially included courtrooms and offices as well as cells. It became for jail use only after the nearby City-County Courts Building was completed.