Could somebody please tell me, if I put a house (it is rented at the moment) that I own outright into joints names with my only son, what would be the advantages or disadvantages
yes, that's (kind of) what I said.
However, if the husnad and son both own 50% but one of them wants to liquidate their asset, the other one might well have to sell
yes bednobs the OP made it unclear if her OH is on the deeds. If he is, and she puts the son on as a joint tenant, then if she died the son and father would become joint owners. If the husband was in agreement and the son was added and they changed the ownership to Tenants in Common, each owning a third, then on her death one third of the house would become part of her Estate.
I wouldn't change the title. I'd do a declaration of trust stating you hold it for you to receive the rental income, the husband (if he survives you) then son absolutely.
It falls outside your estate, land registry doesn't need to know, and if son goes bankrupt or gets married then divorced the asset is not his until the survivor of you and husband die.
I like to thank everyone for all the answers, it’s given me a lot to think about but mainly getting legal advice which I will do. Also Peter said nobody gets any thanks, I wish to add I always thank people on this site. Xx