Leverage the CPA path: Your auditing and financial background will give you an edge when scaling.

Keep in mind, adding "cute", and upgrading things won't increase your rent or ARV past what the market in that area will tell you is the max. 

Longer Tenure in HomesData from the National Association of Realtors (NAR) shows people are staying in their homes for a decade (see graph below):This increased tenure means homeowners benefit even more from home values growing over time.

The increased cash flow would make such a substantial difference in your daily life that not paying it off would be foolish.Outside of that, I can't see many reasons I would take a 15% tax hit to save 4% on a mortgage, which is really only effectively about 3-3.5% depending on your tax bracket.

. - Me, I know the financials.

So building ADU some what makes financial sense. 

Value and rents should eventually increase to turn cashflow positive and build your wealth.You're next learning experience will be, now that you are out of day-to-day management, how will you be able to handle the inevitable expense challenges?

(i.e. a college student with a huge passion for real estate and financial freedom)

We have an existing mortgage (backed by these 2 lots and 2 others) and given the increase in appraised value there is no need to pay anything back to the lender when selling the lot.

.- Working a W2 as a firefighter, posting and consuming content- Leaving my W2 to dive deep into real estate investing and working as an agent... and still watching/posting content all while business was ok - Deleting social media apps (one have one on my phone that I use 10 minutes or less a day), diving deep into building my business and skills which have drastically increased due to pure focus and increasing my business significantly- moral of the story... focus on the things you need to do in business (dollar productive activities) and life experiences while reducing consumption will increase your success