Can I set up a will for a home that has a co-signer?

I am assuming that what you mean is that your mother and brother are the co-owners of the home. The best way for you to set up the transfer would be to have your mother establish a living trust. A trust would allow you to have control over the property immediately without the need of going through probate. Otherwise, the transfer can simply be made through a will, but you would not be able to avoid probate through that process. Jon