The rent a room relief scheme is a great way to earn some tax-free money by renting out a room in your house. Not only is up to £7,500 tax-free, but your lodger is paying down your mortgage for you.
A Lifetime ISA is a way to grow money tax-free. You can put up to £4,000 into a LISA in either Cash or Stocks and Shares, but you can only use this money to buy your first house or for retirement (or incur a withdrawal penalty).