Beyond the financial benefits, this investment also provides an opportunity to spend quality time with my children and grandchildren, as we work together to manage and grow this asset.

The options they gave us were 1) leave the panels in place but get no benefit and do no harm to them 2) purchase the panels (we were quoted the full retail price which is ridiculous) 3) sign a new agreement IF AND WHEN we wanted to.

However, be aware that this might complicate things with the rehab and if you intend to claim tax benefits associated with rental properties.

You also have options like 30 Year Fixed, 30 Year 5/6ARM, 40 Year and Interest only (maximizes cash flow).You are essentially acting as your own bank by using the equity and selecting the best rate/term to benefit cash flow.

It's apparent that you have never been party to a sub2 deal, or given any real thought to the benefits to a buyer. 

Financing can also offer potential tax benefits and help maintain liquidity for future investment opportunities.

What this means is the trustor has zero obligation to the lender past the property in the case of a foreclosure the lender cannot receive any kind of monetary judgment against the owner.. and for the benefit of anyone reading this.. ( I am sure you know what a purchase money loan is.) 

And for the split of the deal you will need to split the equity, cashflow, and the tax benefits.

Any lessons learned from recent transactions that could benefit the community?

It serves many benefits for both buyers and sellers and if a law had been passed long ago that all such private transactions were required to be serviced through a thrid party, we would not have as much regulation addressing the issues we have today, specifically, the individual investors under the SAFE Act!