Synonyms for Kept woman:

n.

brothel, call girl, gigolo, ho, hustle, courtesan, escort, bordello. harlot (noun)
concubine.
kept woman (noun)
mistress, fancy woman.
lover (noun)
paramour.
mistress (noun)
fancy woman, paramour, concubine.
paramour (noun)
courtesan, concubine, mistress, escort.
person (noun)
mistress, fancy woman.

Other synonyms:

harlot
concubine.
Other relevant words:
courtesan, concubine, gigolo, paramour.