I'd have to see your overall layouts but I think you are on the right track. we build 3 story stacked triplexes and it's very efficient so don't be afraid to go up either. anytime you build more than 1 structure costs are much higher but if its just to offset mortgage and you want to be separate then I understand. 

What are the pros and cons of each, and which offers the least restrictions, flexibility and cost savings for my intended purposes?

The property offered a balanced investment opportunity—enough to significantly enhance its value through renovations, yet manageable in scope and cost.

The latter would create mortgage rates issues, the former will eliminate a lot of fake demand and some material real demand in the housing market that is bid side.Mortgage rates higher + build costs higher(less labor + tariffs)= Kill demand.

It's a good practice to overestimate costs and underestimate after-repair values (ARV) to keep your expectations realistic.

More units usually is better, but costs more.

Coin jams are going to be your second biggest headache unless you invest in those fancy ones with tap-to-pay but those cost a pretty penny.

Smart thermostats, in particular, can help you monitor energy use and lower costs between stays.I hope everyone’s experiences and perspectives help guide you as you start this journey!

Having a real estate license, I would credit the commission payed out I would receive for being my own agent towards closing costs for the new property.

I want to know is it more cost effective or easier to purchase the property alone and put it in a mortgage in our name or purchase the LLC from him that holds the property within it.