I am swamped right now with my rental renovations & furnishings I am finishing up plus I typically work late, so I haven't been able to make it much lately.

Refi after construction.These numbers consider only the portion of costs of the HEL attributable to the land purchase, not the payoff of the HELOC (which we took out to buy the Seaside condo).Cash In:                     $66,166 (Cash, 1 year of debt service of HEL, debt service of const. loan, furnishing)Amount Financed:      $548,000 (home equity loan + construction loan + closing costs)Total Cost of build:     $614,166ARV:                               $850,000 (or rather "after construction value")Refi                                $637,500 (75% of value + closing costs)                                        Cash Out                       $89,500New payment             $4500/month (54,000/year)Estimated Cash Flow (pre-tax numbers, so actual mileage may vary)airBNB year 1:            $70,000     (net income $16,000)airBNB year 2:            $100,000   (net income $46,000)airBNB year3+:           $120,000   (net income $66,000)ROI (construction year):    0ROI Year 1 of STR:              24.2% ROI Year 2 of STR:              69.5% ROI Year 3+ of STR:            99.7% Did I calculate these ROI numbers right? 

If so just look on furnished finder for properties in your neighborhood and see what they are renting for.

My mom does not owe anything on it.3)It is well kept, 2 bed 2.5 bath, fully furnished.

Plus doing a quick read did you include all Personal property in the calculation such as furnishings?

I wouldn't necessarily recommend that a family with 3 kiddos go out an buy an STR but since you already own it and have it furnished, its a pretty easy trial.

You make $10k from STR, you have to come up with $22k out of your pocket, not to mention the upfront $100k down payment and possibly another $20k to furnish the house unless you bought it as an existing STR.So in summary, in today's market, it's impossible to buy a STR and be a passive owner and still make enough profit to cover your mortgage payment. 

@Itay Heled  larger properties are not something that is popular with the furnished finder searchers from what I have seen.

The down side is that STRs are more work, need to furnish it, pay for utilities and WiFI but in the right market (vacationers and business travelers) it could work. - If I were looking at cash flow as a really important important metric, I'd consider starting a business.

I agree with the comments above.Most important is a fully furnished, comfortable property with the basic amenities: coffee, teas, functional kitchen (all utensils, spices, cooking and baking, etc.)