Shared house - future plans

Avoirdupois

A friend bought a house jointly, with a chum, years ago. They are mortgage free.  Now as we all getting older, he seems unwilling to face the inevitable.  I have no interest in the house or either of the two owner's assets.
If either of the two owners needs, for whatever reason, to sell or even just move to a different dwelling for example should mobility issues occur, he seems to be reliant on the simple fact that they have a tenancy in common arrangement.  I've tried to advise him that they should at least discuss possibilities and perhaps consider legal advice.  I'm worrying that one or other of the owners will arrive at old age and need to make changes sooner than the other, which may lead to difficulties. Or am I worrying too much?

propertyrental

When they purchased, presumably they discussed various scenarios?

one needs the cash and wants to sell
one gets divorced (or married then divorced) and the ex makes a claim on the property
repairs are needed and one can't pay (or doesn't want to)
one wants to move a partner in
tc etc

What agreements did they reach and how are these documented?

Avoirdupois

I have to say I don't have a great deal of info. so in some ways, it's unfair to ask you, dear reader, to comment!  However, I think it's time I may need to advise my friend to i) open discussions with the other party and ii) consider taking advice from a solicitor - perhaps at the same time as making a will.  Best thing I can do is to lead by example and get my own will written up.
Of course, at the end of the day, my friend's affairs have nowt to do with me.