Hi johacb,
Finding inexpensive rentals online is tough. Dominical is getting very expensive and the places that are more budget friendly are usually found by word of mouth. Your best bet is probably to wait until you get here to find something long term. It’s easier when you know people and can ask around. One other idea is to join the local Facebook groups- sometimes people post listings in there. There’s one for the Costa Ballena Bulletin Board and Costa Ballena Yard Sale Page. You might also look into rentals in Platanillo, Tinamaste, and San Isidro del General. It gets much cheaper the closer you get to San Isidro. Here’s a website with some rentals in that area: http://www.chirriporealty.com/#