Receipt of rent & payment of rent

Sir,

I have a friend who is 72 years old and having residence on the 4th floor of a building where is no lift. Due to his age he is finding difficulty to climb 4 floors and decided to give his flat on rental for around 25K a month and took another flat on rental having lift for a rent of Rs.40K per month. Will somesone advice me about the income tax implications about the income from rent and simultaneous expense  of rent.