The X Factor boyband were placed fifth in Heat magazine's Under-30s rich list last year, with an estimated combined wealth of £26.33 million ($41.72 million).
A source told The Mirror: "Their success is quite staggering - so are the profits coming with it. The lads had an incredible 2012 and this year looks even bigger.
"Although they're all mature for their age, they are still five young boys at heart, and have all made mistakes - it's part of growing up."
They added: "They've now been assigned a small team at one of the country's top money service providers who will be advising the boys on matters of tax, capital and investment.
"One Direction have become one of Sony's biggest draws and the label wants to make sure the guys are looked after."
Earlier this year it was claimed that the boyband would have their own private jet on their upcoming world tour.
The group were reported to have signed a new financial contract with record label Sony which seeks to ensure the band stay together for at least three years.
Niall Horan was said to have bought a a £70,000 ($110,910) black Range Rover after passing his driving test earlier this month.
Photo gallery - the Heat Rich List 2012 for the under-30s