Mr & Mrs S own the house (A) they live in outright (value £275000)
Mr & Mrs S and their son own a 3 bed terrace (B) between them recently bought for £62500 now worth £85000 after refurbishment (never been let).
Mr & Mrs S intend to purchase a new house (C) to live in for £450000 with a mortgage of £337500 allowing them to add houses (A & B) to their rental portfolio.
Although the loan facilitates the purchase of the new house (C) it is "wholly and exclusivley" to allow them to add the two properties to thier rental business (as they could alternatively sell the A&B and withdraw the capital).
What actions do Mr & Mrs S need to take to ensure that the interest is an allowable expense against the rental income generated from A & B?