(Dow Jones) Wayne Blanchard got a call a few years ago from a man in his early 60s, who had lived with--and depended on--his parents for his entire life. The parents had died.

The son didn't work and hoped that Blanchard, founder and principal of Money Professionals Group LLC, a fee-only financial planning and investment advisory firm in Orlando, Fla., could figure out a way for him to live off his parent's $650,000 estate.

No easy task, but this made it harder: The man had obsessive-compulsive disorder, as well as Tourette syndrome. Blanchard's challenge would be trying to secure the future of a client whose ability to make sound financial decisions might be impaired.

In fact, the man thought he was in great financial shape, and was even shopping for a sailboat.

Blanchard calculated that his new client, who didn't feel he would ever be able to hold a job, needed $48,000 a year to live. That meant had to earn a 7% annual return on his inheritance.

"There's no way anyone could generate a safe 7% return in this market," says Blanchard.

Blanchard suggested the client apply for Social Security, which would cut him a monthly check for $600. The move also would make him eligible for Medicare and thus save him $1,000 a month in insurance premiums.

That's when Blanchard got his first real taste of the client's challenges: The man said his disabilities were a secret. He had plans to write a book, he said, and was worried that the government might share the information with his critics, who would use it against him.

Blanchard started to wonder if the client was capable of being helped. He even called his mother to talk over whether he should take him on as a client. But, having dealt with a father and a son with disabilities, Blanchard felt he couldn't abandon this client. In the hands of a bad broker, "he'd be eaten alive," Blanchard says.

Blanchard decided to charge half his hourly rate, and set out to convince the man he was in a serious bind. He tried to verbally reason with him and, when that failed, experimented with a software program to help the client get a visual grip of his financial reality. The software, Money Guide Pro, generates projected returns in chart form.

No matter what asset mix Blanchard plugged into the program, he couldn't get it to project a safe 7% return on investment. He let the client try entering numbers on his own.

"As my client watched the program go through dozens of possibilities," says Blanchard, "it began to dawn on him that it was time to stop sailboat shopping."

With the client now in reality mode, Blanchard proposed they aim for a more realistic 5% return, which would last him until he was 90. "At that point," Blanchard says dryly, "it'll be time for him to apply for a job at Wal-Mart."

The client was willing--but still wouldn't budge on Social Security. Blanchard now knew that, to help a client with this type of disorder, he would have to commit to becoming the man's unofficial financial steward.

So he did. He offered to make his reduced hourly rate permanent. He invested the client's assets in managed funds to further save on fees, and he monitors those funds for free.

Blanchard encouraged the client to enroll in a cheaper private insurance plan, and is looking at other ways he can cut spending. "So far I've found about $1,000 of wiggle room," says Blanchard, "It's not much, but at this point every little bit makes a difference."

Blanchard still worries about the client relying entirely on his investments to survive. "The irony is that I'm more worried than him," says Blanchard.

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