Oh for goodness sake, I have never heard such crap.
1) Whilst the house has been "willed" to Joko, there is no guarantee she will get it. Wills are only workable if they are updated regularly. Much could happen between now and Joko's parents' deaths. (Joko - please do not take offence at this next bit, it is for illustrative purposes only). One parent could die and the other could remarry, thus invalidating the wills. Or one or both parents could need long term nursing care and need the property sold. Joko has a "spes" or "mere hope" of inheriting. Then even if she does there is the potential for inheritance tax or capital gains tax to be paid. It is clearly her parents' intention of leaving it to her, but at the moment, it is just that.
2) Whilst I can understand (to a point) the concern (although I don't understand the vitriol), can someone explain to me the difference about Joko renting a house off an unrelated landlord and claiming HB for the time when she is out of work - knowing that one day she may inherit property from her parents?
So presumably the problem will be solved if Joko moves out, rents another place off an unrelated landlord and pays her rent/HB to him that solves the problem? In the meantime, Joko's dad takes in an unrelated tenant. How on earth does that change things financially?
By the way, can someone remind me of the law that says "if you have a hope of inheriting property sometime in the future, you are not entitled to benefits"?
And Joko to answer your question, as long as there is a tenancy agreement and a market rent, I do not see it would matter. However, to make sure, I would contact your local housing department for advice. Most take the view that as long as the above is in place it is fine.