St. Martin is not generally associated with budget accommodation, given the supply-and-demand dynamic of such a small slide of paradise. Also, can depend hugely on whether you're traveling on- or off-season. You might try to look for timeshare units that are on the market for one-off stays. Otherwise, I'm a fan of HomeAway.com for its extensive inventory of vacation-rental units, including 610 in St. Martin/St. Maarten when I was researching this. VRBO.com is another site you should search, which also lists dozens of vacation-rental units in St. Martin/St. Maarten, too.