Elizabeth Profit has won some tournaments for 18-year-olds, even though she's only 13. Younger sister Mary has enjoyed similar success playing up, even though he's just 11.
"The girls are like sponges," said the sisters' tennis coach, Dave Nowick. "They're eating up everything. They're eating it up because now they're getting feedback that is producing results. The results that we're getting now are unbelievable."
What makes the Profit sisters unbelievable is their drive -- not just on the court, but to the court.
"This RV was not in the plan, but the thing is, when we got an apartment, we were never there," said the sisters' mother, Yvonne.
"Since it's so small and there's not that many doors that you can lock and you can go in, so usually we just, when we get mad at each other, one will go in the bedroom and I would go in the bathroom and lock the door," said Mary.
Yvonne, a single mom, doesn't just drive the RV to and from practices and tournaments. It's also their home.
"The RV, it's OK," said Elizabeth. "I just want to have something that doesn't have wheels and a steering column. [Mary] told our mom, 'I'm tired of living in a rectangle.'"
This "rectangle" is where they study, often stopping at the library. The sisters are home-schooled.
Yvonne said that when she bought the RV, in essence she bought more time for the girls to train.
"When you don't have a great deal of money, you have to improvise," said Yvonne. "So, I'm a learned woman, but I'm also a frugal woman. I know that I have 'X' amount of dollars, so I have to use this money wisely."
Some might question the decision to spend what little money they have on private lessons, but Dave Nowick coaches them for free.
"I thought what they were doing before was, technique-wise, bad. Now we're going to put together a game for them," said Nowick. "We're going to put the strokes together behind all the talent they have -- court positioning, smarts on the court -- and put this whole thing together."
But life has also served up its share of challenges for this family, including 13-year-old Elizabeth's daily battle against diabetes.
The RV enables them to easily monitor her insulin and to keep it nearby and cooled.
"Heck of a challenge," said Yvonne. "Elizabeth wears an insulin pump, the Omnipod. What happens is she's played in tournaments. You only have so much time in order to do a correction. She has gone so low, no matter what I put into her, it doesn't elevate her blood sugar."
Yvonne, a Michigan graduate, gave up a career of designing databases for telephone systems all so her daughters, ranked in the top 10 in their respective age groups, could pursue the dream of becoming professional tennis players.
"It's a choice that I made. I would die for my children. They expect me to give 100 percent as a mother. I expect no less from them."
This "sister act" is surely being steered in the right direction.