Hospitable is the easiest and most intuitive.

I personally have used a few spreadsheets in which the layout changes way more often than it should and is very much a work in progress!

Bonus points if the lender can do const finance and then final occupied financing.To get that, you'll need:1) Figure zoning out and how many you can or want to build2) Go to architect and builder and get a sway on layout and costs3) Most painful, go to the governing entity for permits and pay your soft costs. 

It's straight forward and intuitive and it gets it done.

These are inexpensive and very intuitive programs that won't overwhelm someone just starting out.

Sure, pictures are always best aren't they  :)To give you an idea as to the house layout, the floor-plan has one full bath upstairs, and the two baths you see in the image below ("Current Configuration"). 

But as with renovations to the kitchen, use your budget on superficial changes versus major modifications to the layout.

I liked how the property was meant to be a duplex and the layout feels natural.

I'd love to jump in if there's reasonable amount of risks that I can recover if anything goes wrong, but my intuition says I might be crossing a very dangerous bridge, which is seeking hard money lender to start BRRRR without much money in my savingsI'd appreciate all advice that you guys could comment.

At least 5 or 6 buildings, similar unit counts and layouts.