Hardy said Notts were losing £1.6m a year when he took over in January, but insisted the club was making progress off the pitch after having put things right on it.
"It is step in the right direction, but it is still a lot of money we are losing every year. The whole business model has to change," Hardy told BBC Radio Nottingham.
"While I am thoroughly enjoying it, the challenge is immense. It is made very special by the success on the pitch and the great job Kev has been doing, but it has been hard work.
"I don't regret it, but it is much tougher than I thought. I am having a great time - and it helps that we have been successful. If we were in the bottom two then maybe it would be a different story.
"But this is five-year plan and it will be five years before we break even. We have to do more off-pitch stuff, more commercial stuff, to support the football side."
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