Sec 266 and adding property taxes to basis

In 2018, house is occupied by beneficiary of estate, form 1041. In 2019 person got evicted. In 2018 about 10K in property taxes was paid. No filing requirement in 2018 because zero income. Can the 266 election be made to add the prop taxes to the basis of the house which was sold in 2019?

Questions: if someone is living in the house in 2018 without paying anything does it fall under the definition of "unproductive real estate"?
The person living there in 2018 is one of 10 beneficiaries. That may make a difference.
No filing requirement for first year. I understand that the election should be made on an original return. Is this an issue because no return was filed for 2018?
It's unclear to me if I just add the 10K in property taxes to the basis in 2019 when the house was sold, without attaching the statement for the elections.

Questions: if someone is living in the house in 2018 without paying anything does it fall under the definition of "unproductive real estate"?

Maybe, but what about the improved/unimproved question? I may be wrong, but it my understanding that the property must be both unimproved and unproductive to capitalize property taxes.

Yes, I found some more info on it and it sounds like it only applies to unimproved vacant lots.