I also am aware of successful househackers around who rent bedrooms out of larger homes.And also cash flow is just one component of buy and hold investing.

Whoever purchased at $540k is way too close to the ARV of $610-625k.Someone already ate up most of the value-add component of this deal, did you get this from a wholesaler?

I could probably take apart these single-pane old windows and handle restoring every wooden component with new wood myself, replace the pulleys and rope, bring the windows back to what they were originally.

As far as adding them to rentals, having solar might not matter to renters in lower-income areas, but I'd also suspect that higher-income, higher-educated tenants might pay a slight premium to live in a more environmentally-friendly building, or that building would simply be more desirable to tenants.

I would simply find some environmentally friendly weed killer and (most importantly) deterrent.

Houses and land are unlike other assets because they so often have a huge emotional component attached to them. 

If the economy is strong then we all win, regardless of any one individual component of the tax code. 

The framing and floor components do need to be signed off by an engineer.Also, when you say you are planning on more new builds are you planning more builds ITP?

If you want an environmental impact, I suggest demanding people be celibate; it’s population pressure that’s killing the planet, not diets.  

Most investors I know looking back there with these interest rates aren't budging unless there is meat on the bone as there still is a work component to this model and its not for everyone.