Yes, it is possible to live in Boracay for a month for about 20,000-30,000 pesos (US$ 500-600+/-) for 2 persons. How many of us would want this? A normal hotel accomodation in Boracay can cost like 15K-20K pesos for 3D/2N per person. If your not particular or sensitive about travelling alone or not really conscious about luxury and all of those stuff then choose a hostel or room that is safe and clean.
This is how you do it.
Rent: Hostels usually offer room rates from 8,000 pesos to 15,000 pesos per week or per month. Negotiate with the owners or better have a local negotiate for you. Other high end hostels costs much more. There are locals that live in the island that offer their rooms to would be travelers. Just be wary about security.
Food: Hostels also offer communal kitchens where you can cook your own food. There are plenty of wet markets and several groceries in Boracay to choose from. Also there are cheap ‘carinderias’ around offering meals from 50 pesos to 75 pesos. While well-known fastfood chains have from 100 pesos to 200 pesos. Most hotels also offer eat-all-you-can buffet dinners starting from 200 to 500 pesos. High end hotels offer eat-all-you-can buffet from 800 -1500 pesos.
Transport: Going to Boracay and staying there for a month does not entail going by plane. Unless your willing to spend then go by plane. Going by boat is the way to go. Daily trips from Batangas port to the port of Caticlan is good via 2GO Travel. They offer varied accommodations while on the ship. Rates start from 1200 pesos one way. From Manila, go by bus to Batangas port. Its a 2 hour bus ride depending on Traffic. 2GO offers free bus fare if you book through their booking offices. Its cozy and safe. They usually leave Batangas Port by 9pm and arrive at Caticlan Jetty Port (Cagban) by 6am. Just sleep in the ship. Dinner and Breakfast is offered in the ship. From Caticlan port (Bangka trip is 25 Php, 75 Php environmental fee, and a 100 Php Terminal fee – as of 2013), ride a Bangka ferry to Boracay Jetty port. You can be in Boracay in less than 16 hours.
Inland Transport: Tricycles are plenty from 20 pesos. Or just walk around. White beach is more or less 4Km long. Walking around Boracay can be done in 2-4 hours.
Gym: There gyms there that offer 50 pesos per day. It means you can work out in the morning and evening by just paying 50 pesos.
The rest of your budget? Its up to you on how you want to spend it. ATM is all around the island. Bring enough cash as you can safely bring. Credit cards are also honored in most hostels and restaurants except carinderias of course.