Your question sounds like you should contact the Agency on Aging to begin your journey. The twists and turns involved in the beginning stages; your sister condition, history, overall financial status, Doctors evaluation, living conditions. It is important to reduce the steps necessary to "get on track" and get a solid start.
I'm not familiar with the term housebound assistant. Is that a Veterans Administration (VA) Pension term? or Are you referring to a caregiver? Need more information to provide assistance.
If Garden is correct in what your question is be very careful of companies such as what she provided the link to as often they charge sums of money to help. Call the VA to ask questions like this. Their staff have been very helpful to vets that are entitled to benefits.
Assistant? Asset? Assist?