91 year old mother deeding home to son

1) Do a title check: you want to make sure there is not some lien (e.g. form not paying a contractor or from being sued) or a mortgage/HELOC/reverse mortgage which you are unaware of, and which will impact your rights to the property. Have a title agency do this for you.
2) Similarly, be aware that if there is a mortgage, etc. on the property, it cannot be deeded to you without paying it off.
3) Consult with a CPA or accountant about the potential tax impact on both you and her of her giving you something worth tens of thousans, if not hundreds of thousands, of dollars. Generally, taxes have to be paid by either giver or recipient on such large transfers.
4) Be aware that if she is doing this to try to shield her home from Medicaid, it will not work: the state can void or undo transfers of property made for less than their fair-market value (i.e. when you don't pay the fair value for the home) if the transfer occured less than 5 years before your mother needed Medicaid. The law lets the state void transfers made within this five-year "look back" period to avoid people from defrauding Medicaid by hiding asserts or giving them to family and friends.