There are other niches of REI that you can utilize to raise capitol for additional rentals/properties, example: flipping properties, note investing, lease options.

Both ideas have a hint of validity, corner it, focus your thoughts on what you what, create a niche and believe in yourself and soon you will have the magic potion. 

- This is more of a technical question. 

Technically, hard money is not cash. 

I think you don't technically *need* junction boxes, like you do for 120 V and up, but if you put a splice behind the drywall, it will fail about 5 minutes after you get done painting the drywall

Do not commit mortgage fraud.Fannie Mae has a renovation program available to investors, but for SFRs only.Renovation loans are a niche product, there are loan originators that ONLY do renovation loans and others (I do this, but not in your state) that'll do the cookie cuttie reno deals and refer you to a specialist if it's non-cookie-cutter.

You might consider Niche or Specialized Housing like student housing.

You may be able to paint stone in a faux stone sponging technic that would not destroy value, but I wouldn't be brave enough to try.

This house is technically my primary residence, so I'm assuming we were allowed to complete most of the repairs without any of us being a GC or licensed?

I think your ideas are good - it sounds like this couple do have value to add (some capital, labour, technical skills, and maybe most importantly, time).