Working 2 jobs at once - is this wrong?

So ‘a guy I know’ works in the insurance industry and has built a really nice resume and techical skillset. So much so that he probably receives 20-30 unsolicited invitations to interview with other companies per year. Occasionally, he will look into one further and typically receives an official offer which is polietly turned down.

He has currently positioned himself nicely with one of the big hc insurers in the country and is 100% telecommute. However, he still likes to go into the office a couple of days per week to grab lunch with friends and keep a finger on the company’s pulse.

My pal recently took another of the big insurers up on an invitation to interview and was extended an offer later the same day. Sensing their enthusiasm, he threw out a number much higher than offered thinking this would kill the deal and he could keep doing his thing. Well it turns out that company #2 came back with an offer which contained a salary & bonus structure greater than he initially countered with AND it is 100% telecommute if he wants.

That brings me to this...

My bud thinks he has the bandwidth to perform both jobs, and job #1 has flexible hours which could be utilized if necessary. However, the companies are competitors and would never allow this. It’s not necessarily unethical, because the jobs support different markets within the country, but job #1 and job #2 can’t find out about each other, or he’d surely be blackballed.

On the flip side, my pal is super intrigued by the money and - if he could just make it ride for 2 years - he could pay off his house and stick another 6 figures in the bank.

What advice should I give him?