They may get to travel the world but the job isn't without its perils.
Two years ago, for example, the father of Bernard Tomic, one of the most hyped players in the last decade, was found guilty of assaulting the player's former hitting partner, Thomas Drouet.
Now, one of the longest lasting relationships -- and one of the highest profile -- has come to an end.
Sascha Bajin, a constant in Serena Williams' life the past eight years, suggested on Twitter earlier this week that he was no longer working with the 19-time grand slam winner and has instead begun a partnership with Williams' friend and tennis rival, Victoria Azarenka.
Williams wished him well.
Their split was confirmed by Williams' agent, Jill Smoller, in an email to CNN.com, and Azarenka's coach, Wim Fissette, confirmed that Bajin is indeed the two-time grand slam champion's new hitting partner.
They practiced together for the first time this week.
"I'm very excited about having Sascha in the team," Fissette told CNN.com in an email. "Sascha is a great guy ... and has so much experience in working with Serena.
"I saw Sascha hit many times so I know he is just a very good tennis player. To give the player the best rhythm is extremely important.
"On the other hand I think it's very good there is someone else in the team with experience winning grand slams. That's always very important. Sascha knows what it is like to be in semifinals and finals in grand slams."
No one has disclosed what led to the parting of ways but Bajin wasn't with Williams as she won the Australian Open in January. Bajin said he was injured, with Frenchman Jonathan Dasnieres de Veigy replacing him.
Fissette, who was formerly alongside Kim Clijsters, Simona Halep and Sabine Lisicki when they either won or reached grand slam finals, said he was "very surprised" that Bajin became available.
"Sascha was working so many years with Serena and I felt they had an excellent relationship, more than just player and hitting partner," he said. "I felt they were very good friends.
"But it's not my business to know what went wrong. Maybe they both needed a new challenge. I think everybody will remember the many years they worked together and the excellent results she had during that time."
Williams, about to make her return to Indian Wells
after a 14-year absence, once likened Bajin to a brother.
"Outside of my parents, I think he's probably the most important person on the team," Williams told USA Today
in 2013. "He's much more than a hitting partner. He's my older brother. He's family."
Bajin's alliance with Azarenka serves as another change for the Belorussian. Azarenka split with coach Sam Sumyk -- who quickly moved on to Eugenie Bouchard -- and hired Fissette in his place in February.
Azarenka is attempting to recapture top form after foot and knee injuries derailed her in 2014.
"From the first meeting, I felt a good connection (with Azarenka) and after the first two weeks I feel a very good connection," said Fissette. "Vika is very motivated to get back to the top and wants to become a better player. That is what I feel on court and I believe it can be a great year for her.
"I believe it's also great for women's tennis that Vika is back. She is a great tennis player and an excellent entertainer."