However, he wants a new security deposit and a month's rent for the
time we will use it in March, claiming that the sale process makes us
new tenants.
What are the legal rights and legal obligations of an estate in a
month-to-month rental situation? The estate is just starting the
probate process, and I am unclear on whether the landlord is a
"traditional" creditor or in a unique situation since the money he is
owed for rent continues to accrue after death.
The decedent's security deposit, less valid deductions, is property of the estate, so if the landlord takes a second security deposit he is double dipping.
Generally speaking, after someone dies, money judgments that have not been reduced to judgment liens, and unsecured debts (i.e. debts not supported by collateral) only have a right to be paid via submission of a claim to the probate estate in the probate process with claims made paid according to a priority schedule set forth in the probate code.
But, generally speaking, death does not impair the property rights of third parties, so the fact that a debtor's estate is in probate is usually not a basis upon which a foreclosure or repossession of collateral for a default on a secured debt, or an eviction due to the termination of a lease, may be postponed while the probate case runs its course. Probate does not have the equivalent of the "automatic stay" in bankruptcy that prevents any creditors, secured or unsecured, from engaging in any collection activity against an estate, and probate estates are not allowed to file for bankruptcy either.
If you really wanted to play hardball and only needed the apartment for a few days in March, the estate could simply continue to occupy it for that period of time and they pay the landlord the extra month's rent but not the additional security deposit when it was done. The landlord can't begin a foreclosure proceeding until there is a default which can't happen sooner than the last day of February. Even if the landlord is really on his toes, the landlord will be hard pressed to get a notice to vacate served on the estate and then to prepare and serve an eviction lawsuit on the estate and get that case in front of a judge before the estate will be ready to move out anyway. The estate might incur some attorneys' fees in the process if it did that, but the attorneys' fees would be an unsecured claim of the landlord that would have to be collected through the claims process in the probate proceeding which is usually a fairly favorable forum for the estate, instead of the usual court where small landlord-tenant disputes are handled. The probate estate could simply deny his claim for attorneys' fees and then, if the landlord wanted them after making a claim, the landlord would have to bring a lawsuit on fairly tight deadlines in the probate court to have the disallowance of the claim overturned.
If you wanted to be even more aggressive, rather than paying the last month's rent, the estate could just holdover into March without paying rent or a new security deposit (vacating before the eviction process can run its course), effectively forcing the landlord to use the security deposit for March rent, and then forcing the landlord to use the probate claims process for both damages to the property claimed and for an attorneys' fees. If the estate is insolvent, or if the claim wasn't filed by the landlord (who may not even know that it is necessary to file a claim in probate) within the short deadline for probate claims arising after death, those expenses just wouldn't get paid at all.