Is adding a ADU worth it?

[Andrew Ellison]

My 45,000 square foot property in Maili, Honolulu, is zoned R20. 
I have tentative approval from the City and County to subdivide. 
My question, is adding a ADU to the front property, already has a single family home on it, worth the cost of the build, how much value would the ADU add to the overall value of the property?

It would be an owner builder exercise and I could build the 800 square foot ADU for less than $150,000.

The ADU will be positioned so that it will not encroach on the set back requirements of the pole lot at the rear of the property.

Appreciate any suggestions and comments.