Your concern is genuine. This is a usual problem. It is good of you to think about welfare of your elderly and ailing parents. I wonder whether you can appoint a full time care giver.In absence of an alert person in the house,they are likely to be the victim of hoodlums or any manipulator.
I was also faced with similar situations some time back and I came across this Article that gave me a lot of advice to help me out. It gives advice on Life Insurance for People Over 70. I believe you would find it very useful if you check it out. They provide good services such as quotes and have support team that will attend to you.
Check with your local county/city whatever where you live for a senior service center. The county I live in in NJ has a senior center near me, and I am out in the country (not is a city). I do not know what services are offered but I think giving advice on services for seniors is one.
The unfortunate answer is to have a court hearing to establish guardianship. There are many degree of guardianship from simple management of all finances to complete control over medical care and housing. You need to do a google search on the guardianship protocol for your state. There is a problem with the senior service centers. The invariably refer the case to adult protective services. This covers their butts. A case worker from APS will visit without notifying you, and generally a psychiatrist from APS (again without notifying you or permitting you to see the diagnosis). They may initiate a guardianship procedure and you will find yourself on the outside, looking in. The guardianships are often political plums dealt out to connected social workers who bill $200 an hour for "investigation" which the judge orders to be taken from the seniors bank acount. I have been involved in several guardianship procedures, and the best outcome is when a relative initiates the action.
I am so sorry that you have to walk through this. I see that you are my baby sister's age. Our parents died when we were pretty young. At 58, my sister is still raising one daughter who's about to head off to college, but she doesn't have aging parents to be concerned about. I never did either, and I'm sure it's frightening and horrible to see them begin to fail. But may I say that you are wonderful to be there for them to offer help and support to them as best you can. You're a million times blessed, and you will not regret it ... going forward in your life, you will not regret the time you've given them now at the end of their time on earth. I do agree with caregiver222 that it might be time for you to establish some guardianship or conservetorship to protect them from fraud. There are plenty of people and companies eager to separate old people from their money these days. This is a tough time for you, and I'm so sorry for it.