The mother is in failing health. She is the sole deeded owner. Should we have a life estate deed or her only son as co-owner?

I am not licensed to practice law in MA, but most states allow the use of a "beneficiary deed" which allows real estate to pass upon the death of the owner without the need for probate. Of course, you would want to make sure that all other assets are pay on death or you are named as beneficiary (i.e. you don't want to fix the real estate to have your mother pass owning a CD in her individual name - requiring probate). I don't encourage joint ownership of property between parents and children due to liablity concerns and the loss of a stepped up income tax basis realized on the passing of property from a deceased person to his/her heirs.
I hope this has been helpful.