This
FAQ lists timeshare rental sites. The problem with renting a t/s for a whole month, if you're trying to stay in the same unit, is that very few of them are owned for a whole month by the same person. If you don't mind moving half way through, you should be able to find something there. Renting a hotel room for a whole month probably would be fairly expensive, as in dead high season, they may not discount it at all from the daily rate, even though it's a rental for a whole month.
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