I will definitely take a look at that site. 

Also a good stand of teak about 14 years old.There are two house sites possible.  

Your best bet is to read information from public blogs that approach both options objectively.

See this BP blog for a numbers comparison - More Units Doesn’t Mean More Money—Why a Single-Family Home Can Beat a Fourplex.Stay focused on your goal, financial freedom; not following popular dogma.

Rob just updated everything...here is the site he tells everyone to visit for STR cost seg.STR Cost Seg

There are a million sites you can look at to get an idea based on more parameters.

See below:Survey (8-10 weeks) Request Permit Prints from Design Team (4-6 weeks) Site Plan and Septic Design from Design Engineers. (6-8 weeks) Need survey back to start designs as this is site specific Energy Docs (1-2 weeks) Need plans from Design Team to make request.

Quote from @Kyle Luman: I just listened to the recent BP podcast with Dr Benjamin Aaker and Dave Meyer from a couple of weeks ago.https://www.biggerpockets.com/blog/real-estate-1045There was a section where Dr Aaker talks about focusing on equity and trying to avoid cash flow since he didn't want more income presently while earning money as a physician. 

Hire an inspector /independent person to manage the job site for you, someone with your best interest at heart.

For something more robust, tools like Excel or online calculators from financial planning sites might better suit your needs.Your ROI Formula:ROI = (Net Cash Flow ÷ Total Out-of-Pocket Investment) × 100For your scenario:Net Cash Flow = Annual Rental Income - (Mortgage Payment + 401k Loan Payment + Other Expenses)Total Out-of-Pocket Investment = $40,000 cash + $50,000 loan payments over 5 years.I came across a piece in Bloomberg recently discussing creative financing, and they touched on ROI calculations for multiple loans.Personal anecdote: A buddy of mine leveraged a 401k loan for a fourplex.