I don’t know the rules, but after much consideration we gave our contractor the go-ahead to do it on a remodel of our two story primary residence in Sherman Oaks back in 2004.

Vegas hasn’t grandfathered any STR properties after they outlawed them in Clark county and changed the rules in Las Vegas. 

Even if you have to sell before the 2-year mark as required by sec 121 rules because of health, work, or some unforeseen circumstances, you might still able to avoid tax.

I have been using the BP calculator using real numbers and rules of thumb.

I plan on doing this with my long term friends they are all financially stable and have jobs and the income to support the move.

I would make sure the work already done was inspected including whatever supports the second floor.

Will you be affected by the new Salem AirBnb rules taking effect in April?

Income Evaluation No of Units Unit Rate Income       2 Bedroom Unit A 1                 650.00                                    650.00           2 Bedroom Unit A 1                 650.00                                    650.00 2 Bedroom Units A 1                 650.00                                    650.00 2 Bedroom Units B 1                 650.00                                    650.00 2 Bedroom Units 1                          -                                               -   3 Bedroom Units B 0                          -                                               -   Garage Units 0                          -                                               -                  -   Storage Units 0                          -                                               -   Laundry Units 0                          -                                               -   Comm Units 0                          -                                               -   Comm Units 0                          -                                               -   Comm Units 0                          -                                               -   Total Monthly Income 5                                    2,600.00 Total Annual Gross                              31,200.00 Total Annual Cost / EBIDTA                                9,911.86 Net Cash Flow (Annual)                              21,288.14 Net ROI 42.39% Monthly Cost of Operation By Landlord By Tenent Monthly Annually Monthly Taxes x                                       137.50             1,650.00   (From Historical Data) Montly Space Rent (MHP)                                                -                            -   N/A Monthly Insurance x                                       100.00             1,200.00 Calc'd Monthly HOA                                                -                            -   Posted Monthly Water/Sewer   X                                       320.00             3,840.00 Estimated Monthly Garbage X                                       160.00             1,920.00 Estimated Monthly Electrical X                                                -                            -   Tennant Monthly Heat/Gaas   X                                                -                            -   Tennant Monthly Other Utes x                                                -                            -   N/A Monthly Yard Maint x                                         20.00                 240.00 Estimated Monthly Maint - Op Ex x                                       260.00             3,120.00 Calc'd - 10% Cap Ex x                                       260.00             3,120.00 Calc'd - 10% Monthly Vacancy x                                       182.00             2,184.00 Calc'd - 7% Screening/Tennant Management x                                         20.00                 240.00 Estimated Monthly Management x                                                -                            -   At Risk - Self Manage MONTHLY OP EXP                                   1,459.50 Total Annual Expenses                                 17,514.00 Total annual Debt Service                                   8,452.36 Net Operating Income NOI                                 13,686.00   Net Income                                       5,233.64 ROI % 10.42% Low/Average CAP Rate (Net Income/Purchase) 2.92% Extremely Low  Cash Flow per Door                                       109.03 Very Low  Tax Assessment  Estimated Expenses - 50% Rule                                       159.50 Conservative Banked Amount - CAP Ex, Repairs, Vacancy                                   8,424.00

If your planning on using the land for an additional building, I would call the local planning dept and make sure that the property can support it.

They did all kinds of crazy stuff back in the day, so I don't rule anything out.