My mother needs guardianship papers but where to start?

Depending on the extent of Alzheimer's, it may be too late to do any type of POA. Original poster asked about Guardianship so I suspect she needs info on that.
Lawyer office (elder care lawyer) is the only place that can help with that.

First of all I want to tell you to hold on to your faith . . Take a deep breath. There is POA, Medical Power of Attorney and guardianship. I have a mother and a mother-in-law with alzheimers. Both of their situations are totally different. I was blessed working with both family physicians and bank institutions that knew me (and knew that I was genuine). It does help! Good luck to you & God bless!!!

If your Mom does not NEED guardianship please do not go this route.
As a wife, if her name is on the deed to the house and the bank accounts there should be few problems.
She should obtain POA for finances as well as health.
there are 2 Guardianship's that occur..Guardian of the Person and Guardian of the Estate.
With Guardianship she will have to get approved by the court any money she uses for his care, clothing expenses as well as submitting documentation on visits to the doctor and the type of care that he is getting.
All receipts will have to be saved and they will also be submitted.
You/she will have to go to court several times a year to present this information. (the lawyers can do this if you wish)
This will continue until his funds are pretty much exhausted then she will become Guardian of the Person not of the Estate
Once she becomes Guardian of the Person an Annual Report on the Ward is filed. This can be completed easily and mailed in.
(Just finished filling out the one I have to for my Husband.)
I think it is insane that I had to "charge him" rent, for electric, food etc in order to withdraw money from his account to help pay bills.
Please talk to an Elder Care Attorney to determine if this actually NEEDS to be done or will other methods be better.

Guardianship is covered by state law, so the procedures and necessities can vary from state to state.

Since attorneys are expensive, you might want to start by contacting your local Area Agency on Aging and asking for advice. They may be able to refer you to local resources that will provide information on what's involved in obtaining guardianship in your area, or under your circumstances.

I believe that in my own state of California, there needs to be proof that the person has lost capacity to manage certain types of affairs, and the courts do need to be involved. But as I said, things vary depending on the jurisdiction and the circumstances.

Why does she need guardianship? What does she need to do that she can't simply do as his wife? My husband had dementia and I never needed guardianship. I'm not trying to argue that she doesn't need it. I'm just curious what the circumstances are.

When I applied for -- and was awarded -- guardianship of my mother I took the steps pamstegma advises. The court order was not granted in a courtroom; just a small office. The person who granted the order asked me only one question, "Why do you want to be her guardian?" Answer, "Because she's my mother." I was awarded control of her finances, and required to keep written accounts of what I spent on her behalf.

You start with your family attorney. Guardianship is granted by a court order. She has to petition the court for guardian/conservator status.