I've suggested for years that employer implies to a houseboy that he will be paid for services, (even if it may be in trade for room, room & board, etc).  In an effort to ensure that this doesn't turn into an escort site I've asked for the title to be reconsidered again, but the suggestion back is that I should post it in the forums to be discussed.  When doing an internet search for "Antonyms for house boy", two titles come up:  boss and master.  I've placed a few examples in a poll to see what others think as well!

I usually refer to "employers" here as hosts. There are several obvious reasons an employer shouldn't stipulate sexual activities as a requirement for employment, but a man that hosts a houseboy can provide certain amenities to a houseboy staying with him in exchange for certain benefits offered by the houseboy in return. The details are, of course, between the host and the houseboy, but there isn't really anything wrong with hosting a houseboy that happens to enjoy willingly being sexual as well.

i have also fallen into using HOST.  MASTER only makes sense for kinky folks.  some kinky people say SIR.  no one ever says SPONSOR.  i call people BOSS but it rarely gets used in the third person.