So the lot size is not much of a constraint especially with new offset requirements for 2020.Now my question is strictly from the financial point of view, how do I go about deciding the size (sq.ft.) of the ADU?

@Oleg Enik I totally see your point of view.

View report*This link comes directly from our calculators, based on information input by the member who posted.

View report*This link comes directly from our calculators, based on information input by the member who posted.

When viewing comps you need to make sure your houses are comparable... meaning similar layouts and styles.

My view is that you should decide on a strategy first as they are two different business models. 

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Our opinions of what is "good" may vary so I'll refrain from labeling the deal as such, since some people view good as $500/month cash flow and others would be happy with $150/month.Some people want their money back in 7 years, 3 years, 15 years, etc.Have you accounted for maintenance and vacancy?

@Cameron Tope You may be right about shooting the idea down, I wasn't sure how they would view it since there was no actual cash flow yet, would they consider that theoretical rent into DTI?

For HouseHackers, Loan Officers, and anyone with expeience using either of these loans: what's your view on using a 3.5% down FHA loan vs a 5% down Conventional loan?