Finding a Place to Rent
While I don't handle rentals, some real estate brokers here in Sullivan County do. But there really isn't a central clearinghouse for broker-handled rentals. While the Multiple Listing System has the capabilitity to include rental listings, often brokers with available rentals don't put them in the MLS. Whether you're looking for a full-time, year round rental or a seasonal vacation rental, the best option is to identify the brokers in the areas you're interested in, and call or email them individually to ask about rentals they have available. Unfortunately, the Sullivan County Board of Realtors doesn't post a list of members, so you'll have to Google for individual Realtors, e.g. if you're interested in a rental around White Lake, Google "Real estate brokers White Lake NY."
Property Managers:
But if you're looking for a vacation rental, you may want to search through some of the websites that typically have rentals listed here in Sullivan County.
Vacation Rental Websites
Sullivan County Visitors Association Cottage Lodgings