Roger Federer has racked up millions from prize money, sponsorship and endorsements throughout his legendary career but his children can seemingly expect no handouts.

The 20-time grand slam champion is among the wealthiest sports stars in the world, yet while their dad is playing at the Indian Wells Masters his four children have earned pocket money through an age-old venture... a lemonade stand!

While the resurgent world number one defends his title in Indian Wells, Federer's offspring have been quenching the thirsts of neighbours at their rented home for the tournament.

And Federer, speaking to Tennis Channel about his living arrangements for the Indian Wells-Miami double header, revealed his twin girls Myla and Charlene, and twin boys Leo and Lenny, had made a tidy profit from their business venture.

"So, we've rented a house [for Indian Wells] for many years now. We like it this way here," he said.

"We then stay in a hotel in Miami. You get used to certain routines, especially with the kids you like to know where their bedroom is ahead of time.

"But here it's jumping in the pool, selling lemonade on the side of the street. They made $70 yesterday! It was classic.

"Unfortunately, I missed it because I was here all day. But they had a great time. All the neighbours are very generous to the kiddies so that was a lot of fun."

Federer put on a sparkling display to defeat Filip Krajinovic 6-2 6-1 on Monday and book a last-16 date with Jeremy Chardy.