I have meticulously designed, built, decorated, furnished, cleaned, stocked with hotel-like essentials, cleaned again, and published my property as a vacation rental on AirBnB.

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. 

My other unit has a washer with the mechanical controls so it'll be interesting to see which one lasts longer.

My background is in mechanical engineering and am currently an Engineering Manager in the medical device industry.

Some improvements can be less obvious like mechanicals, electrical and plumbing.

I would have never thought about getting into buying a car wash, but what attracts me to this situation is that he really knows the ins and outs of mechanically making sure these things run well, and he also can walk in and tell immediately whether the equipment is in good shape/ has been maintainted.

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.