It is unlikely you can build a detached ADU of this size and quality, not doing the work yourself, for $80K. 

- Is there a way to improve quality of the tenants in short term of 1-2years? 

Housing prices (SFH, MF, and apartments) all can vary depending on neighborhood class, size/location, time of year you're trying to fill it, quality of finish out, etc.

I've finally decided to get more active with my RE investing endeavors and make quality connections with people in this community, through meet ups, discussion forums, and mastermind groups. 

I planned on getting a quality home inspection.

Last, the pre-finished hardwood is pretty affordable when you consider the relative cost of lower-quality products and the fact it is pre-finished so, nail it down and your done.

One thing you can do is to check out the contractor's other ADU builds, you can see the quality as well as ask for permit and final approvals of those projects to verify.Good luck!

You can name whatever price you want, but unless people are willing to pay it then you’ll be out of luck.Also, careful about charging too high a price relative to properties at a similar quality level and area.

Message them- and see who manages their properties and how they would rate the quality of services.

Remodeled with quality finishes. 2 bedroom 3 bath in highly sought after area of University Town Center.