Rental arbitrage involves leasing a property on a long-term basis with the landlord's written consent, then subletting it for short-term stays on platforms like Airbnb. Your profit is the difference between your total booking income and all costs, including rent, bills, cleaning, platform fees and maintenance. A single unit typically requires £5,000 to £10,000 or more in upfront capital for the deposit, furnishing and a running cost buffer. The main risk is void periods: you still owe the rent whether or not guests book, so cash flow management is critical.