It should never cost that much for a single family home.The other thing to think about are tax implications. 

If I do find an insurer willing to do ACV, is the move to document all systems and agree that they are within 5 years old (they are) as I understand ACV has depreciation implications when dealing with a partial loss and set the ACV to around $350,000?

I am a Norwegian citizen, but I have an American social security number.

That changes tax implications.

They have tons of videos on YouTube that are designed to help you with a wide range of social situations.

I am learning, learning, learning the best options for my IRA and understand the tax implications before I jump in.

I was 22 and making just under 30k/year in the social services field. 

Like Cody, I am also not a tax professional, however, Bigger Pockets has a solid blog post on this particular subject if you haven't seen it already. https://www.biggerpockets.com/blog/2016-02-21-tax-implications-house-hacking

I trust the friend and don't think anything would be an issue (although I'm sure people have horror stories about trusting friends) 2a) I'm hoping to not invalidate my home insurance and unsure if having someone stay and pay rent (either above board or cash under table) will screw things up if I have a claim. 2b) Should I have him take out his own renters insurance in one/both scenarios 3) What are the tax implications of both signed lease and cash under table?

My wife and I are investors and flippers in real estate. We’ve been with a local RE firm for almost one year, as agents. As investors we’ve bought, fixed, sold, and kept real estate. We continue to invest, but now hav...