You must know far more than I do about the tax concessions available to business and corporations, seeing as to my knowledge they are minimal, although there is an awful lot of what is now called 'fake news' surrounding this and has been for decades. I work as a corporate tax manager advising SMEs (small and medium enterprises) how to correctly calculte their tax liability, ie many items of expenditure are not allowable for tax. I have been doing this job for 20 years and sadly certain sections of the media have always perpetuated this myth.
As far as tax on rental income for an individual goes, if the property was sold there would be investment income in the form of interest or dividends and this would be taxed - so tax would be payable either way.
The current climate is to tax let property heavily, so the tax on rental properties has increased in recent years (stamp duty land tax premium, disallowance of loan interest etc) as it is considered by those that claim to know that this is artificially inflating the house price market.
As far as
@Kikki21 10% admin charge goes - I think that is worth asking OPG, as if you didn't do it you'd have to pay a management agency the same money and it seems fair enough to me, taxable income for you and a tax deduction for your mum though.
I've come across very succesful AirBnB lettings, some of our clients have switched their properties over to this as they were letting more succesfully, but it does require the input of fresh linen etc so a admin charge by you sounds sensible. If the property is in the right place I would expect a much higher return via Airbnb than a conventional let.
(just seen your last post
@Kikki21 which you posted whilst I was typing)