Why is Sir Toby living with his niece?

Sir Toby is what we would call a freeloader. He has nowhere to live, so he lives with Olivia. He has no money to support his affluent lifestlye, so he takes advantage of Sir Andrew. He also tries to play matchmaker.... choosing on the wealthiest of men for his niece, in the hopes he can set himself up with a nice nest egg in the negotiations.