He will fill out I-130 on his spouse behalf and sign I-864 saying that he is financially able to support his alien relative. He will also file out G-325A for biographic information. If he is married before, get the divorce paper that his former marriage has been terminated.
Once your mother fills for GC application, she will be legal subject to the interviews.
Do you actually know this man, btw ? What if he gets abusive to your mother in the future ? There are many ways to stay here, marrying an old guy she can't communicate with at all will be a huge pain. And your mother barely knows him, how do you prove that this is a real marriage ? When the USCIS interviews them, they would have a hard time to pass !
Good luck.