Cobra is expensive and only ggod for 18 to 24 months.
If they do have existing insurance, they should be able to get into another health insurance company with no prexisting health problem causes.
Any way you put it, buying the house is a good idea, but divide their assets up with those that are trustworthy to protect them in the advent of a massive medical issue.
One other thing, considering speaking to an attorney specialising in asset protection. My parents have done so as I am the only child left alive and my Mother has terminal cancer. While I will not delve into the specifics, I do know that they are covered quite well should she be "dropped" by the insurance company and medical bills bills being to high for them to be able to cover it and not lose any of their land, home, or investments.