Mortgage With A Co-signer Who Is Terminally Ill

TLDR: FIL is my cosignor on my mortgage, I have a 2.59 interest rate. Cancers a bitch, when he dies, how do i do things like take out a home equity loan if and when I need to. I still have 23 years left on my mortgage and the house is already 26 years old. I hate that I have to even think about these things.

So, my MIL and wife inherited a house from GMIL that was fully paid off, that netted us about 250k after we sold it. My in laws were retiring about the same time that I got a job that took me across the country. So we decided to take 200k and use as a down payment on a larger, nicer house for all of us then use the remaining 50k to put an addition on for my in laws. I had the income and my father in law had damn near perfect credit, So we consigned the mortgage together. According to my Mortgage company I have about 250k in positive equity.

Here is my problem. Cancer is a bastard and 3 months ago my FIl received a terminal diagnosis. I feel awful even thinking about these things, but the house is 26 years old. I need to be pragmatic. This is our only asset, I have no real savings to speak of due to stupidity when I was younger. We have an amazing and probably never to be seen again interest rate but We need a new driveway (one of the trees we had removed earlier tore the driveway apart so it floods, which brought in a sink hole like thing that causes the driveway to smack the bottom of the cars and move like a teeter totter) the AC works great but it’s the original one and when we need repairs it’s getting harder and longer to find parts and we have dead trees that hang precariously over our house and quotes to replace all of these things separately were 4-5 digits.

As far as the mortgage go, I will continue paying like I do, so that’s business as normal. But how do I tap into the equity if and when I need to? Do I need to talk to him about it before he passes or do I have options after? I don’t want to be backed into a corner in a few years where my only options are refinance the house or take out an unsecured loan. If I open a Line of credit against it now, will it even stay open for that long or would I have to use it now ish or lose it?