Much of what you read or hear has been exaggerated by the media. Visitors will have no security problems provided they use a little common sense and avoid leaving valuables around etc. You only need pay for the percentage of the course completed. If appropriate, you can obtain a referral which means that you can complete your course at any PADI recognised dive centre world-wide, in your home country for example.
Skilled workers can earn a lot more.
At the other end of the scale, there are a number of Filipino businessmen who are wealthy by International standards. I notice that several dive sites have sharks. Much of what you hear and read about sharks is nonsense. Divers in the Cebu area see sharks on a regular basis and have never experienced any form of attack or threatening behaviour. In fact sharks are rather timid and often swim away if they see a diver approaching.