If you could take the roof off your condo, then pick up the unit and turn it upside down, everything that would fall to the ground is personal property. Personal property is not an integral part of the dwelling structure and is depreciated on a five year schedule.
Reading between the lines, you bought the property in 2016 and furnished it for your personal use. In 2019, you converted the property to a rental. What is not clear is whether your rental use was only for three months and the property is now held for your personal use once again. If the property is still in service as a rental, you are allowed to depreciate the personal property using its depreciated value (or thrift shop value) as your depreciation basis.
You can't use your cost because after three years of personal use, the value of that property has declined through age and wear. In this instance, I would not bother with the personal property depreciation until it had to be replaced. At that time, depreciation to full cost of the replacement personal property item or expense if one of the safe harbor rules apply.
