The idea
Remove Building Society restrictions on renting a room and 2nd room in a house which are as follows:
a) Apparantly one would have to involve a solicitor for 1st room if permitted to rent in the first place
b) One wouldn't be allowed to live in the house if one was renting a second room as it is classified as a business.
Due to restrictions some people rent a 2nd room covertly not because they want to avoid tax but because they could get into trouble with the building society.
However as the vast majority of people have interest only mortgages (I know this due to the fact I worked for a well known Mortgage Lender) they would be probably liable to very little tax in their now rent rooms business as you can offset the tax against any profits you reap.
ALTERNATIVELY
Alternatively due to the small amounts of tax involved in renting a 2nd room scrap the tax altogether and raise the threshhold.
Why is it important?
Free more rooms for renting and help ease the financial burden which is on families today due to lack of jobs. Also less people would require family credit as their income would increase and more tax revenue.
ALTERNATIVELY
More money for people to spend hence some businesses would flourish.