Pretty-routine technical stuff...maybe you really trust someone who has a similar one-man show, and could have a "cover each other's backs" agreement. Though that can get d*mn tricky pretty quick - say, when there's a tax return due, or your clients are asking what's going on.
Really good friends and family could try to cover for you, within their skills. But they may be too busy already with visiting you in the hospital & making medical decisions & maintaining your house & etc. etc. etc.
Especially for SaaS-type stuff - where your clients can't just hire some other lawn service, and your family can't just sell off the mowers - you need to have a real "worst case" plan, so that nobody's left SoL.
I know that sounds dismissive, but really what is the point in continuing to drive marginal capitalistic value after you’re dead? If it’s to take care of family, the answer is a single member saas company is not a good vehicle for intergenerational investments/cash flow. In that case, work in exit/diversification plan and execute it while you’re still alive.