(In the simple / non complicated scenario)- time ranges - in the best / simple case scenario how long should I expect this process to take? 

I think I would probably talk to an attorney tbh these business purpose non regulated loans do not have rate locks that have to be honored legally.. they can and do change them unilaterally.. borrower accepts counters or declines and loan fails. 

He has only done single family (non investment) properties.

These are typically 'non english-speaking' neighborhood so to speak for political correctness. so parking while already become a problem, but adding ADU in that neighborhood would not become a problem because 'everyone knows each other' everyone has their own unit.But that ADU thing, is bit uncommon in 'english-speaking neighborhood' LOL, so that's where "some" people is complaining about parking space and so on and so on when one home is building ADU.For me, I prefer to have ADU on the hill side, now we have 15 car space and from one neighbor to next neighbor is like quite distant.

A 4 bed, 1 bath is typically a non-starter.Improving kitchens and baths.  

Following advice, I put $130K into a charity fund to start a 501(c)(3) non-profit.

I was advised it would be beneficial to have a reason for non-renewal in New Hampshire in the event that the tenant fights it.

As I mentioned above, the risk of being sued, found guilty, and fined more than your insurance will cover is almost non-existent. 

If you think there might be the possibility of development raising the value in the future, you could try renting out the property to others for non-intrusive uses - parking, roadside vendor, etc. 

If they are on different tax parcels, I will use DSCR for the non-primary deals and then FHA or UDSA (assuming it is rural) for the owner-occupied one.