There is a wide range of accommodation in Rarotonga, it is always to start looking early if your on a budget or want to reduce your cost's.
Private houses are plentiful however the quality ranges from very basic to luxury accommodation.
When looking at a place interior island houses can be cheaper and some come with a pool, one tip though chickens and Roosters are plentiful so be warned early morning crowing can be the thing "take your earplugs if your a light sleeper".