The booming property market has spawned a whole new industry for letting apartments and houses and the big agencies are determined to get some of the action. Sherry FitzGerald and Gunne have opened new letting departments, while a whole bevy of companies have sprung up around the city and suburbs. Apart from the good fees to be earned from letting homes - Sherry Fitz has pushed the letting rate to 7 per cent - the agents also pick up more business if the investor finally decides to sell. Similarly, investors who buy through them will be encouraged to use their lettings departments. The number of letting agencies has shot up but many of them are feeding from the same trough since canny landlords place their properties with a range of agents. Whoever lets the house or apartment gets the fee.