What exactly is it that you'll need money for? I understand that his finances are complicated and you'll need information to sort them out. Has he already granted you power of attorney in his will? If so, as much as it won't be a fun conversation, I'd sit down with him and ask him for detailed paperwork outlining all his assets/finances, and his wishes for them when he passes. As far as what you'll need money for.... attorney, funeral.... anything else? If you'd be paying the premiums on his life insurance policy, you may be better off just investing that money instead so you'll have it set aside when the time comes. Since you have no way of knowing when he'll pass away, maybe you could invest in something like a CD so the money is earning a little more interest than a regular savings account, but will still be relatively liquid. It just seems that at his age and in the absence of an exam, the premiums will be so high that your money might serve you better in another way.
It's nice to be important, but it's more important to be nice.