He is worried that if anything happens to me he will be out on his ear. How do I go about adding his name to the mortgage? Is it expensive and would I be better writing a will?

You are better off with a will. If you split up they can't demand half of what is your now... and in a will they inherit it in a manor that is beneficial to them. And like I said... if anything happens before you pass... you can always change the will to suit the situation.

Adding his name to the mortgage merely means that he will be responsible for paying back the loan. It won't give him any ownership interest in the property. He would need to be added to the deed in order to have any ownership interest.

Whether you add him to the deed or make him the beneficiary in your will depends on your personal situation (ages, children, taxes, etc.). It might be a good idea to speak to an accountant or an attorney (or both) before making any moves.