Well, I get up in the dawn and I go down and lay in the shade
I ain't nobody's house boy, I ain't nobody's well trained maid
-- Rollin' and Tumblin', written and sung by Bob Dylan.
In England, and especially its former colonies, a houseboy is a male house cleaner, or housekeeper. A man hired to clean and do other general tasks around the house. As it turned out, this was usually a white person hiring a black (or shaded) person to do their chores for them. As this term refers to wealthy white people paying local men very little to do their dirty work for them (and then calling them boys, to top it off), the term has a somewhat negative, exploitative connotation.
Americans hijacked the term during WWII, when the troops discovered that they could afford a bootleboy (or batman if you're British); local boys were available to do chores for them for a very reasonable cost. These boys employed by the low-ranked soldiers were called houseboys, and were originally encouraged by the American and British armies. In later wars the hiring of local help was sometimes frowned on, as it meant that a low-income, non-patriotic local could come in possession of information that the enemy could bribe or coerce out of them. If you're not certain if your army allows houseboys, check with your ranking officer.
In the army, hotels, or other situations in which there are multiple houseboys in some sort of formalized setting, there is also often the position of head-houseboy, a houseboy that oversees the other houseboys and takes care of some of the more high-responsibility tasks, like keeping the household expenses and training new staff.
In my researches, I have come across the interesting site www.houseboysusa.com; this site arranged young males (all at least 18 years of age) to work as in-home assistants to older males, with the likely expectation of sex. This type of position is often spelled houseboi to help clarify matters. Sites of this sort are common enough, but I couldn't find anything for females who might want their own houseboys.
I've been getting some feedback about where this term is still used -- apparently it is no longer used in Australia and New Zealand, although it was until the early 1900s. It's not used in South Africa, where the term garden boy may be used with the same meaning. It's still used in India and Thailand, at least occasionally. It seems to have moved into the South Pacific after WWII, where it was quite common; I don't know if it is still commonly used in that area these days. And it is still used occasionally in America, although much less than it was in the past.