What do Britain's Queen Elizabeth, soccer star Wayne Rooney and Hollywood director Steven Spielberg all have in common?

Each is the proud owner of that ultimate status symbol of the wealthy -- a race horse.

Along with wine, art and gold, thoroughbreds have long been the luxury investment of choice for the mega rich.

But the industry appears to be taking a new direction as an increasing number of "Average Joes" pool their money and head to the sales.

"Owning a race horse is more accessible than ever before," says Richard Wayman, chief executive of the Racehorse Owners' Association.

"At the top end, you've got huge international buyers paying millions of pounds for the best bloodstock.

"But in recent years, lower down, there's been a proliferation of people becoming part of a syndicate."

A fairytale buy

For Australian lawyer Colin Madden, buying a thoroughbred with his friends six years ago was the most extraordinary -- and profitable -- decision of his life.

The 54-year-old had known nothing about horse racing, describing himself as an Aussie Rules Football man, when his mates suggested buying a horse.

"We saw it as an excuse to have a laugh," Madden told CNN. "For us it was a shared experience with people we liked spending time with -- we never really expected to make any money from it."

The five friends, some who had known each other since kindergarten, pooled their money and bought a thoroughbred worth $315,000.

Little did they know, the mare, Black Caviar, would become the most successful sprinter in the world, unbeaten in a staggering 23 consecutive races to date and winning more than $7 million in prize money.

The six-year-old celebrity horse has not only earned big money on the track, she's become a lucrative brand -- appearing on the cover of Vogue, launching a range of grooming products and publishing a best-selling biography.

Risky business

But despite his spectacularly lucky investment, Madden had a word of warning for those considering purchasing a thoroughbred: "Never buy a horse thinking you'll make money."

"Success is 10% bloodline, jockey and trainer," he said. "The remaining 90% is good fortune."

Owning a race horse offers prestige, excitement, and a unique insight into the industry. But if you're looking for a guaranteed return on your investment, think again.

"Putting money into buying a horse is a risky proposition -- you never know how good it's going to be," Wayman told CNN.

"There's always the hope as an owner that you get a horse that can compete at that top level. But I think that's more of a dream than reality."

Thoroughbreds range from $1,300 ("You're very lucky if you buy one at that price and it wins any race. It's a bit like buying a used car," said Wayman) to more than $3 million.

And that's just buying the horse. By the time you pay for stables, feed, trainers and jockeys, the net return is around 21% -- meaning for every $100 you spend, you get just $21 back.

What to look for

"Always look for a thoroughbred with a good bloodline," said Madden. "That way, even if the horse can't run, you can always breed them or sell them off. It's a type of insurance."

And if champion British thoroughbred Frankel is any indication, sometimes the biggest money can be made off the track.