You can't purchase insurance unless an insurer is willing to sell it to you. However, you could petition the probate court to administrate the property and have title transferred to the bona fide heir(s) -- whomever they are. If one of them is your mother, then you could simultaneously seek reimbursement from the estate for the value of your improvements, and assuming that you prevail, the court may order the property sold to recover its value so as to pay your claim.
This could lead to a settlement, under which you would share title to the property (to avoid selling the property) -- and of course, once your name is ***** ***** you can purchase insurance.
It's certainly not a convenient process, but if you really want to protect your interest, then you need to get the legal "ducks all in a row."
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