hotels aren't really set up for anything except shorter stays. But,I would recommend you contact olas de oros villas, cabarete villas, nanny's estates, punta de oro apts, ali's apts/surf camp, casa blanca and check out l'agencie in town for rentals. Gerard at El Magnifico also manages apts/houses on the beach. You can also get cheap housing with backup electricity in the dominican neighborhoods...
I usually recommend people go stay at a hotel for a week, and look around for themselves.