Assuming you live in the United States, you need to be aware of the laws in the state you live in. Many states are one party consent when it comes to recording. Which means if you and I are having a conversation, you can record it without telling me. One party has consented.
If on the other hand, you install a camera without your mom's knowledge, then you are not one of the two parties. This "evidence" could be thrown out of court as it is "illegally aquired".
Not to say you shouldn't do it. Protect your mom's property. I would just suggest looking into the local laws about it. I am also not a lawyer so you should look into your local laws or consult a lawyer.