Typically, the property converts to personal use the day after the last tenant moves out. This is because you have specifically made the decision already, to not rent it out again as supported by you notifying the tenant of the non-renewal of their lease, as well as not actively attempting to rent it out upon termination of the current lease.
Any repairs done after the last tenant vacates the property are for personal benefit, and not for the benefit of the next paying tenant. Therefore those repairs are not deductible. So do as many repairs as you can before the current tenant moves out and ensure the date of the invoice/receipt is dated before the property is vacated by the tenant.
Now property improvements are an entirely different thing. Property improvements either retain or increase the value of the property. For example, a new roof is a property improvement. New windows are a property improvement. But replacing that broken deadbolt on the front door is a repair and not an improvement since it does not retain or add value to the property.
Now any property improvements done after the last tenant moves out will add to the cost basis of the property. But you will not enter those improvements done after the last tenant moved out, anywhere on your tax return. That's because the improvement will not be placed "in service" for the purpose of producing income. You simply file the paperwork for said improvements with other papers related to the acquisition of the home and they won't come into play on a tax return until one of three things happens in the future.
1) You convert the property back to a rental
2) You sell the property
3) You die.
The basic difference between a repair and a property improvement:
Property improvements are expenses you incur that Improve, restore, or otherwise “better” the property. Basically, they retain or add value to the property.
Repair expenses are those expenses incurred to return the property or it's assets to the same usable condition they were in, prior to the event that caused the property or asset to be unusable.
