Illinois has some new incentives that the solar-owner would retain. 

No retainer needed - but pay someone to review your docs and make sure you are current and compliant with state law.

The board of county commissioners shall have the authority to cancel any contract if the purchaser fails to comply with any of the terms of the contract and the county shall retain all payments made on the contract.

Typically rent is not earned until the month it is due, so should be retained in a prepaid account, and/or accounted for as unearned revenue until the month it is earned.

You will need to retain some of your profits for taxes on the flip.

I know there a lot of different names for this strategy including Land Contracts and Installment Sales Contract but my understanding is that the seller retains title to the property until the buyer, or investor in our case, pays off the loan amount agreed upon.

I find that I learn and retain knowledge better in hands-on scenarios.

Call the numbers for the leasing office s and ask about the area, ask about how their experience is getting and retaining good tenants.  

In order to avoid the low participation rate, I've a.) suggested that by completing the survey, the tenants could win up to $100 - the amount is a function of the thoroughness and comprehensiveness of their answers and b.) issue the survey with 3-6 months left on the year-long lease so that I can take the feedback into consideration and assess repairs and improvements that may help retain my top quality tenants and reduce vacancy. 

Alternatively, you don't have the increase to her portion, if you want to retain her.