I have been contemplating between Arizona area and Bakersfield.

Ask about what the contract arrangement, how did they do on budget, time, what problems did they encounter and how did they overcome them, how was communication (daily, weekly) and in what format, what was the estimate of work, how did that estimate compare to other estimates.If you want to mitigate risk, then first you have to build a relationship with your contractor on less riskier projects. 

And I'm trying to understand what arrangements (and range) are more prevalent in mid-scale (say 1.5m post upgrade) real estate.

They've been here for a few days, and inquired about making arrangements to stay in my vacant unfurnished room with an air mattress. 

That alone is a pretty solid contract.Of course it's a great idea to "paper up" to make sure everyone is covered, and would definately be the better setup for a long term arrangement.

Plan was to make high-end rental units with some exposed brick, in-unit washer/dryer, off-street parking, tile shower, solid countertops, etc.Mistake 1: I had a local architect make building plans involving a floorplan change for a new bath/kitchen/master bedroom with walk-in closet arrangement in the rear of the units.

So I would follow him being he said he was going to arrange another one soon. 

For those funds we work with that do allow leveraging, we normally skip the bank and arrange the line through institutional lenders.

You will probably want to hire one to draft up a contract for the arrangement anyways.

Caveat: in virtually all LOC arrangements, be aware that the bank will be able to "call" the line of credit at any time.