From what I know of you frigator, you are retired and have a modest income from private loans and you have found that revenue from that source is increasingly constrained. Meanwhile, like most of us posting here, you have acquired a laudable level of wealth that permits you to struggle with wants and not needs.
I could be i n a similar situation, though retirement is in my own hands and I m pulling in 6 figures while working. When the gravy train ends, I will be similarly situated and likely looking for a new abode and making a decision that resembles your own - so for me, your dilemma is actually one that gets me to think beforehand.
What I know given my own experience is that I would prefer a situation of debt that is easily assimilated into my current lifestyle - that would likely mean paying some 50% in cash and assuming the remainder in a mortgage. Mortgage rates are very good right now and I think even playing solid, conservative, low-growth dividend companies will produce yields comparable to any 15 year mortgage (say 3% roughly). If you had an equal amount in Proctor and Gamble or Clorox some other very conservative dividend player and it didn't appreciate in capital gains, it would wash out the cost of your mortgage interest.
So I would try that. I don't think all debt is bad and some measure of debt is actually functional as it permits you to maintain a credit score for subsequent purchases that require some debt assumption. Plus the interest on your mortgage would tax deductible and that is a small advantage to consider. All in all, it may be an advantage to assume some debt as it can be written off, maintain your credit rating, and be an amount that doesn't challenge your current lifestyle.