There is no typical day for a firm of private investigators, no two days are ever the same. When the phone rings you never know who will be at the other end, it could be a law firm wanting a professional process server to persoanlly serve legal documents or trace hidden assets for one of their clients. It could be a private client who wants their husband/wife followed because they have suspicions that they may be seeing someone else and therefore require expert surveillance operatives to discreetly undertake observations and report back what the subject has been doing.
Alternatively it could be a company who has issues with one of their employees such as long term sickness. It could be that the company is concerned that a director is passing on confidential information to a competitor in return for cash and they need to have Private Detectives to uncover the truth. The company may need a computer forensic service or debugging or require a background checks to be implemented on an individual. When the phone rings it could be a radio station who have a presenter who wishes to discuss with a real life private investigator what it is like being a PI.