I thought I the only rule that needed to be satisfied to avoid capital gains was that  the purchase price of the replacement properties had to be of equal or greater value.

Type of ADU Assumed SF Price/SF Total Cost Sample Monthly Rent in Oakland Valuation Net Equity Shipping Container Conversion to Modern ADU 160 $ 300.00 $ 48,000.00 $ 1,500.00 $ 216,000.00 $ 168,000.00 Garage Conversion to ADU with existing foundation 500 $ 300.00 $ 150,000.00 $ 2,000.00 $ 288,000.00 $ 138,000.00 Garage Conversion to ADU without existing foundation 500 $ 400.00 $ 200,000.00 $ 2,000.00 $ 288,000.00 $ 88,000.00 Basement Conversion to ADU with existing foundation 500 $ 300.00 $ 150,000.00 $ 2,000.00 $ 288,000.00 $ 138,000.00 Basement Conversion to ADU without existing foundation 500 $ 400.00 $ 200,000.00 $ 2,000.00 $ 288,000.00 $ 88,000.00 Detached ADU with traditional prefab modular 500 $ 250.00 $ 125,000.00 $ 2,200.00 $ 316,800.00 $ 191,800.00 Detached ADU with modern prefab modular 500 $ 350.00 $ 175,000.00 $ 2,300.00 $ 331,200.00 $ 156,200.00 Detached ADU with on site build easy access 500 $ 300.00 $ 150,000.00 $ 2,200.00 $ 316,800.00 $ 166,800.00 Detached ADU with on site build difficult access 500 $ 400.00 $ 200,000.00 $ 2,200.00 $ 316,800.00 $ 116,800.00

It may be worth it if you never have to replace a roof for example.

Planing to replace 20 year old roof on Single Family home size 1800 sqft. 

The windows are all ancient and need to be replaced.

Two days later we were informed by the tenant that the gas was shut-off to their respective space served by the package rooftop units whereby portable electric baseboard heaters were purchased and brought in to provide temporary heat until such time a final decision could be reached as to whether to repair/replace the existing package rooftop units.

All new new drywall and paint in a 4000 sq ft home, flooring, replaced all plumbing and upgraded electrical, new siding and garage doors, 4.5 updated bathrooms, kitchen remodel with quartz countertops and stainless appliances, many windows replaced, we kept as much original trim and doors as possible, upgraded the staircase with fashionable stainless steel cable system.

All new new drywall and paint in a 4000 sq ft home, flooring, replaced all plumbing and upgraded electrical, new siding and garage doors, 4.5 updated bathrooms, kitchen remodel with quartz countertops and stainless appliances, many windows replaced, we kept as much original trim and doors as possible, upgraded the staircase with fashionable stainless steel cable system.

***Its impossible for us to know without knowing all the details, but generally one months fees is not enough to replace CAPEX items.

@Chris Levarek - My plan is to delay financing as I have to start looking for a 10-31 replacement property so I'm more concerned about getting that taken care of.