AS well they are both stable and producing quite a bit of monthly income.

AS well they are both stable and producing quite a bit of monthly income.

Question is: what will produce the best return in the next 10 to 20 years? 

If you have a portfolio of, say, five rentals in your 401k when you are in your sixties that produce $7,000-$10,000/mo in passive income (rental cash flow) - then you simply take the rental income as your RMD without touching the properties.

Since then, she has sent the keys as agreed but hasn't produced the payment as she promised.  

I definitely recommend that you seek out a Certified Cost Segregation Professional so that you are confident in the quality of the work performed and the deliverables produced.

That is what it is all about.It sounds like your property is quite the income producing piece of real estate with multiple income sources.

But, they are structurally separate and both income-producing.

It appears they've remotely shut down the panels as they haven't been producing for the last month. 

How have the property been producing since you closed in 2020?