I have no experience of shared-ownership for older people but do know someone young who has such a property, and assume they are the same thing.
The problem is you'll be paying rent on the part you don't own until you die, or move. This will eat into any capital you release when you sell your present home.
Also, although you will own, say half, you are fully responsible for costs such as if the boiler breaks down - the housing association doesn't pay the other half.
It would be simpler to move to a cheaper property. And why move into something that needs a lot of work doing to it, particularly as you are on your own?