Although Mallorca is a stunning island with an alleged average of 360 sunny days a year, rent is still somehow super cheap and nice rooms, short or long-stays, are relatively easy to come by.
When you first get to the island you most likely will not have already found a place to live and will be looking for some temporary housing. I suggest you check out the Central Palma Hostel located in the heart of Palma. It’s very easy to get to from the airport (for 2,50€ you can take the Line 1 bus and it only takes 15 minutes!) and it’s located next to some of the best spots in the city including an improv theater with events almost every night, fun bars with traditional tapas and outside seating, and the farmer’s market.
When you’re ready to look for something more permanent, LoQUo, the Craigslist of Spain, is your best bet. You can find a nice, furnished room for 250€ with utilities included. I actually found a place in a shared flat on LoQUo before I arrived, talked to my new roomie on Skype who agreed to pick me up in the center of town, and was perfectly content with my new room.
It’s probably a better idea though if you meet your potential roommates in person first before deciding on a place. Couchsurfing is alive and well in Mallorca and every week local members host a Thirstday bash. It’s currently being held on Thursdays at 21:00 at the Molly Malone pub (Calle Monsenyor Palmer, 5). If you’re already in town it’s a great place to have a few cheap drinks, meet new people, and get the word out that you’re looking for a room.