Re: guardianship of a mentally ill parent
As a child of the disabled person, you would qualify to be nominated via POA, see below, of the person as a guardian. This requires that the disabled person has requisite legal capacity which, based on your description, is questionable.
Another option is for you to be appointed by court for a specific transaction (i.e., sale of the property). Or, alternatively you could be appointed as guardian for all affairs. The powers and duties of the guardian need to be carefully considered since there may be other issues that require attention.
Two qualified physicians must provide certified statements that the person is in need of a guardian. There are specific requirements over the physician's certifications. A filing is made in Circuit Court. There is an alternate process available if you are unable to have the disabled person examined by a physician.
The context of this decision often require consideration of more than the obvious matters.
Other than guardianship, the person could give effect to a power of attorney (POA). POAs can vary and I invite you to see other answers that I have provided to questions relating to this matter. One key point to bear in mind is that the person must have capacity to effect a POA.
You should consult with an attorney practicing elder law. I am available at (410) 799-9002.