My Dad has dementia and doctors say he needs 24-hour care. Are there places that help with care that are reasonable or free?

You really need to contact Medicaid in your state to fully understand the rules and requirements. It varies state to state and you want the information that pertains to your location.

They do own their home.  His SS pays a portion of the mortgage and then there is not much left.  I thought Medicaid you had to make $10K or something similar per year as an annual salary?  His wife works as a tutor and may make $50K a year.  We will call the local agency to see if he qualifies but do they take her salary in consideration?
He is Stage 5 with dementia and doctor says he needs 24-hour supervision.

Call your local Area Agency on Aging and ask for a needs assessment; they can point you to local resources.

Have your parents applied for Medicaid? Did the doctors say what kind of care he needs, i.e., nursing home, memory care, assisted living?

The AAA can usually direct you to a social worker who can assist with sorting out what folks are eligible for in terms of aid. Do mom and dad own a home?

Check into Medicaid. Call your Area Agency on Aging to learn about programs that he may be eligible for. For example, if he is a veteran and served during wartime, there is Aid and Attendance available.