It’s definitely possible, but you either need  the ability/willingness to pay easily $1M+ If you want to be in a B or better neighborhood or you have to be fine with living in areas like Richmond or Oakland and rolling up your sleeves on a major value add deal.

Just easier for me, especially having the ability to transfer funds online at the drop of a dime under one phone APP, and to keep track of my expense for tax purposes. 

2) If we refi at a "midpoint," what impact, if any, would that have on our ability to refinance again when the rehab is complete (i.e., when all 17 units are online)?

The lock and your ability to enter are separate issues.

Such as, what is driving the economic growth - which businesses are moving to town, where are apts being build within the market, which part of town is growing the fastest.

Apparently legislators are work-shopping a bill to close this loophole, but who knows on the timeline.https://realestate.cleveland.com/realestate-news/2018/08/big_big_money_legal_loopholes.html#incart_river_index

Assigning a contract you are a principal party to, is also not illegal in any state.There's really only 1 thing that is illegal and is often promoted by wholesale gurus, and that's pretending to be the buyer and telling the seller YOU will buy their house, when you have no ability or intention to do so.

Highly conservative investors will park their money in real estate for safe keeping when they have no use for it such as growth of investments.

I will take the negative too and glean from it. there is no magic formula for this... get a job in the industry earn and learn.. save and then invest.. no ability to borrow basically and no cash will be big time waster for you.. don't waste time on something that is a unicorn and not real. 

His wife has a good job, so I am confident in his ability to pay the money back even if something bad happens to the house.