Looking for a template/excel calculator (rather than building from scratch) to model investment for MF land develoment, buIld and Sale - wIth typical metrics: NPV/ROI and cash flow analysis.

You need to do the analysis cash flow using tool, photos. down payment, interest rate, neighborhood type, condition like every deal posted. 

Before you continue down the modification path much further I'd get in touch with someone who specializes in garage conversions or ADUs and get an approximate price and timeline and run the numbers again, it seems like you may be underestimating the cost, time, and difficulty of a project like this.

@Ahmad Fadhil what is the projected sale price?

Using a conservative rental analysis, $1,400/mo is the rental income. 

Nice project!

Depending on taxable income of the LLC, your dad's other taxable income, projected growth of the business, and your dad's goals for the business, an election to have the LLC taxed as an S Corp or a C Corp might make sense now or in the future. 

To name a few:Base your underwriting on how you will operate the asset, not based on how it is currently operated or based on the broker's pro formaCreate a budget for each year you plan on owning the property + sales assumptionsHave an upfront operating account fund in addition to ongoing reservesBased the market rents on your own rent comp analysis, not the broker's rent comps15% contingency on top of interior and exterior rehab budgetConservative annual income growth assumption (no higher than 3%)

@Michael Bertsch If you were doing some kind of expansive yard project that would prevent the tenant from using the yard then I would give notice, but that obviously is not the case here.

Purchase price: $10,000 Cash invested: $43,000 Sale price: $110,000 Worked on the project from June to December, when we listed, closed the sale on March 1, 2018. 3 Bedroom 2 bath 1600 square feet.