I have decent W2 income and I plan to continue working for at least 5-10 years.

Stage 3 would be financial independence and Stage 4 would be generational wealth.The Mastermind – In general, I am leaning toward roughly Brandon Turner’s model:Highs and LowsTopic/Hot SeatGoals StatusI would recommend one hour and am open to suggestions on this.

@Dan H. answer is detailed and correct.The cost to convert your garage to ADU is not equal to the comparable sales which is what is used for an appraisal.If you want to put your Mom on site to help her and the goal is not for financial reasons it will make sense.

Boston and the immediate surrounds are still the employment capital of the region and people are enduring longer and longer commutes for the opportunity to work in the colleges, hospitals, pharma companies and financial district of Boston / Cambridge.I wonder if there's a practical limit. 

My land is also buildable and I have plans from an architect for a 3 bd/2 ba home which would cost 300k to build (it's in CA) and is in an excellent STR location...but I'd need a construction loan to build it.

I should have my plans from my designer soon and I will show them the plans.  

If I can go with this plan.

I plan to hold it forever, letting tenants pay down the whole mortgage.

How long it takes to be financially ready is different for everyone.

The financial model presented seems overly pessimistic.