Private rental paid up front by a relative

Hello
I'm not sure if this is something that the mods can answer but would appreciate any information. I've also contacted the CAB and am waiting for a call back from them as well.

My brother is currently on UC including the health element whilst he is waiting for a double hip replacement. Following our Dad's death he has to move out of Dad's house and our sister has offered to fund a private rental place for a year whilst he is sorting himself out. The money would be going straight to the landlord (or agent) and paid in a lump sum at the beginning of the tenancy so wouldn't be going into my brother's bank account at all. There will be an agreement drawn up by a solicitor to this effect with a copy being given to the landlord/agent.

We are wondering how to handle this with the DWP. We are assuming that they have to be informed via his online journal, and will be provided with a copy of the agreement if requested. Is it even acceptable to do this or do they count it as income/benefit in kind so my brother's UC would be affected/stopped? It is intended to be a gift with no expectation that it be paid back (this will be in the agreement). We are wondering though if it would be better to be called a loan instead.

Sorry for all the questions and the long post, but my brother is getting very stressed and worried that what is a very thoughtful thing to do becomes a problem with the DWP.

Many thanks and sorry for taking up your time if you can't answer the query.