If you could pickup a junky house for say $10k cash, and you put $10k into repairing it - to a very basic, liveable level - could you deduct those $10k in repairs in one calendar year and depreciate the other $10k over 27.5 years like normal?
Remember I am not really improving the structure, but making just enough repairs to make the place liveable.
A repair keeps your property in good operating condition and does not materially add value to the property. The cost of repair to your rental property is generally an expense deduction.
An improvement adds to the value of your property, prolongs its useful life, or adapts it to new uses. The cost of improvements is recovered through depreciation. If you make repairs as part of an extensive remodeling or restoration of your property, the whole job is an improvement
In your example, to “make the place livable” would seem to require a restoration. The cost of your restoration is an improvement and is recovered through depreciation.
I would add that when the cost of your “repairs” equals the cost of the property, that probably rises to the level of “improvement.”
However… if that consists of a whole lotta little things (A/C maint, floor patch, paint & wallpaper, plumbing fix, new toilet, roof patch, new cabinet door, garage door opener – all that stuff can add up quick) then you can probably get by calling it repairs.
Although you should be prepared to support your deduction. Keep good, detailed records.