How do I know with certainty that an “act of God” or other unforeseen set of circumstances will not affect the private lender’s ability to fulfill their obligations.How do I work out loan advances?

For example lets assume that you have a homeowner who neglects the property and after some years the house needs work (a new roof, HVAC, needs cosmetic work, etc.) lots of equity can be lost due to the lack of upkeep, on top of that as investor you have to purchase at a discount (profit margin).

I also know how any service provider should NOT communicate with their clients (including real estate agents), UNDER NO CIRCUMSTANCES (it is called professionalism) or with any people (it is called kindness, compassion and politeness). 

A change in life circumstance would have to be the catalyst, it seems 

I own a house in Heber, CA, but due to a change in my personal circumstances I will be moving out."

A lot of Midwest properties, especially the affordable ones, have been neglected and are located in less than optimal areas.

But there could be circumstances where a seasoning of less than (or more than)  one year would be appropriate. 

Hell, in normal times in Kane and Dupage Co it could be 2-6 months since the tenant can come and ask for a continuance to get a lawyer and further delay it at least twice then depending on the next available court date it could be another 45-60 days for that case to come back up in front of the Judge, be glad its not Cook Co it would even be worse because of the sheer size.With all that being said, back to your question - there is no quick and easy way, as much as it sucks that he is now 20 days late in the rent count you blessings that it has not been a year plus that you've had to pay for him to live there, which in many cases has been the circumstances.

I imagine the property and the tenants have been neglected; the place will need considerable investment and not all tenants are paying their rent; and that means opportunity.

While technically it might be possible to partner with disqualified person under certain circumstances, this is really bad idea as in most cases this would lead to a prohibited transaction and will disqualify the IRA.