10k was/is the take home pay, considering he doesn't own his own practice anymore then he won't/shouldn't be liable for the insurance expenses.
Your tax figures assume no deductions at all.
It seems crazy to me that somebody could be making 100k+ a year for ~30 years and still not own their own 300k home.
Even somebody earning 48k after tax (median/mean figure for US, apparently) should easily be able to afford their own home after 30 years. No wonder your country is so fucked.
If his skills are interpersonal, I'd stop focusing on the whole dentist aspect and instead focus on doctor patient relationships. In Australia we have some programs that are run by universities to help doctors with doctor patient relationships (how to broach subjects such as confidentially while being sensitive to out clauses such as self harm/harm to others and making the patients feel "safe") - a lot of the stuff is practice - in fact my local high school paired up with the university of Melbourne and we had our drama class act our certain roles and then the doctors in training would practice their med speak. At the end of it the "actors" would give the doctors advice on how they could improve.
I know the doctors in training also did a ton of theory on this type of shit, especially the foreign exchange students that were hoping to get permanent residency.
Might be a niche to look into

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