The main point is that once a person has been sectioned under 117 the local authority has an absolute obligation to provide full aftercare to all intents and purposes for the rest of the persons life.
Very importantly they CAN NOT charge the person or their family for the care it has to be provided completely free.
Obviously, local authorities do not like this, a person sectioned under 117 is going to be in need of constant 1 to 1- 24/7 care. This is exceptionally expensive over £3000 per week is normal .
S117 is a 'last resort' only used if there is virtually no chance of recovery but a person held under S117 can with the correct care live for many years ( at £3000 plus a week!)
Due to this local authorities are desperate to try to avoid paying by any means fair or not, you can expect all sorts of 'dirty tricks' to try to get people to sell homes etc and contribute to care, none of this is allowed see my link.