Green’s Dictionary of Slang

board lodger n.

a prostitute who gives the owner of the brothel a share of her income in exchange for board and lodging.

[UK]H. Mayhew London Labour and London Poor IV 26: Those who are subject to the mistress of a brothel. i. ‘Board Lodgers,’ or those who give a portion of what they receive to the mistress of the brothel, in return for their board and lodging.