Start the conversation sooner rather than later.
If you have reason to think that your parents are likely to need financial or other support, the time to have the conversation is now, while these questions are still hypothetical: Do they have plans for if one or both of them become ill and need care? Do they have the funds to cover care?
Once a crisis occurs—either financial or health-related—planning and reacting are far more difficult. And documents such as health-care proxies, living wills, and other important paperwork should be completed while the affected parties are mentally competent.