Musically flat

My client is a professional musician and self-employed trading in his own name.

He has just agreed a 12-month deal to perform in London in a West End musical and has decided to rent a three-bedroom flat in the city.

His plan is to then rent two of the three bedrooms to other musicians in the show and charge a rent to cover two-thirds of the rent payment to the landlord plus other overheads.

He has the option of extending his involvement in the show for a further six months after the year has expired.

My question concerns the tax deduction against his income for the property costs.

Can he claim one-third of the expenses against his income on his tax return or does he show all of the property costs as an expense and include the rent contributions from his fellow musicians as linked to his...