Could you have them live with you for the last, oh... 20 years of their lives?
If my 'rents were still alive, I'd be okay with that, because they were awesome. Then, again... I'm lucky.
Here's why I ask: Long Term Care Insurance, or LTC, is becoming more difficult, and more expensive to get.
Basically, LTC is a bucket of money to pay for a nursing home, or assisted living center, or for someone to come into your parents home and "help out." NO GOV'T PROGRAM DOES THIS!!!!
Now, RuckingInsurance.com does NOT market LTC. IMHO, you need a full-on financial planner to work out the numbers in the best way for both you, and the parental units.
Have the conversation... or, get ready for a new roommate(s).