She is a graphics designer and makes pretty good money, while also grinding most nights and creating an Etsy portfolio for passive income in the long run.She is very hesitant in buying a Duplex.

Until then we continue with 1970's design.

The property has a small 522 sq foot SFR that is designated as an HPOZ contributor, and our client is looking to build a new modular home about twice the size on the large lot and convert the existing SFR into the ADU. 

The only reasons I can think of why someone would do this is A: They realized they are way over budget and are heading for a loss, they want to recoup their investment and move on, leaving someone else to deal with it. or B: they are catering to designer investors who just want to put their finishing touches and design on the property without having to the nasty demo work and such. 

They are hugely different in many, many ways.Learn the big three:1 - Market Analysis2 - How Money Works3 - Learn what is, and how to design and stay with, your REI plan.I hate to tell you this, but most of the statements you've made are backwards. 

And Carvana offered less than $500 for my 2006 Dodge Grand Caravan with only 66k miles - a car I can sell locally for $4k+ all day long.

Lots of experience and analysis has to go into that decision and even then the highest and best use does not often match up with the current or future designated land use plan for the city or the county. if that's the case you then have to look at what WOULD the city or county approve for zoning and the site plan and figure out highest and best use with return for those parameters.    

The online courses are less designed to help you know all things real estate and more designed to make sure you know the laws around what you can and can't do as an agent. 

Different designations mean different things around the country. 

It also helps that I have friends that hold the CFP designation that I can bounce ideas off of.Right now the OOS markets that we are looking at specifically is Indy.