First - so sorry about the cancer diagnoses. I understand why you feel you want to live your life to the fullest. And I think if we root around in your numbers and think creatively there might be some way to free you up to do that.
On the practical side - can you give us some more information on your properties? Are these houses or apartments? What are the mortgages on them, the interest rates on those mortgages, and what is the rental income? How about anticipated repairs (i.e., how old are the roofs, how much do you anticipate in maintennace costs etc, how much is property tax and insurance etc.?) How long until those properties are paid off?
We need those numbers in order to give you sound advice.
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Also, I like the idea of taking a year sabbatical, then going back to work (maybe part-time). There are ways to travel cheaply (check out
www.couchsurfing.org ), and foreign countries where you could live quite nicely on less than $1200 a month. How much could you rent out the property that you live in now for? Would that additional rent boost your income to enough to live in a foreign country? Would you consider that for a while?
I'm not sure how university fits into all this. How would you pay for it? Would it be with the goal of going back to work in another field? If not, then why not just audit classes or take free classes for the fun of learning.
Do you have any hobbies that you enjoy that could bring in a little income? Or would you be happy just doing a little side job like dog walking to bring in a little extra cash? At your level of spending, just a few hundred extra could make the difference.
Also, definitely be careful about the insurance business. You cannot afford to be without really good health insurance.
It sounds to me like you may need to refine exactly what it is that you want, and then get creative about how to get there. Is it that you don't want to keep working in a job you hate? Or just that you want more free time to play? Are you running FROM something or TO something? If you could design your ideal lifestyle, what would it look like?
If you could get by until the properties paid for themselves, would you be set for life? If so, can you find a way to enjoy the life you want to live while working part-time, maybe after a year of cheap travel?