Annexe guest accommodation planning permission

[bsul]

We are proposing to build an annexe in our back garden to use as guest accommodation. We have a friend who wants to stay there pretty much full time for the next year or two, which would be rent free. In effect she will be our guest.

I do not think we need planning for an annexe, but may need building regs. However would there be any problem with someone staying there rent free? Are there any other problems we may encounter?

The building would fall within criteria for an annexe and would not be visible by neighbors.

Thanks for your help.