Caller said his clients fall into three basic categories. First, there are rich families who want to supplement their children's schooling with added subjects and help them with homework. Second, there are families who have children with special needs, where home schooling is more effective.  (Read more: A surprising group stands in way of income equality)  Many of his clients, however, fall into the third category: rich families that travel between multiple homes around the world and don't want to be tied to one location because of their children's school. Some of these families are also so rich and famous that their children would be mobbed at a regular school.  "They may be based in New York, have a boat in France and a house in Mexico and in South Africa, and they want to use them all," Caller said. "With home schooling and a tutor, they can travel wherever they want and still get to be with their children."  Caller said the tutor he placed for $400,000 a year was for a rich family on the West Coast. The student was having trouble with school and with substance abuse, so the tutor had to home-school the student and coach the student and his family through rehab.  (Read more: Will the Grim Taper be a body blow to the wealthy?)  Caller said the job was "quite challenging," but the tutor also received an apartment, a car, dinner every night and first-class travel.  Hannan, who is currently tutoring in Barcelona, Spain, said he's worked in nine countries over the last seven years and his travel is usually "to great places and great environments."  But being a tutor to the rich has its downsides, Hannan said.
The world's millionaires and billionaires are seeking at-home teachers to help their children in the education race. For the tutors, it's a lucrative business.