Cleaning

Mechanism
You can have an unlimited number of friends. This feature allows you to clean the structures on the islands of your friends. This doesn't affect your friends' islands at all, you just gain XP and dollars :) (This also has nothing to do with facebook friends, it is just internal within the game)

Why should you do that ? Wow, then I have unlimited income with unlimted number of friends ?
 * You earn for each cleaning the amount of XP according to your level, e.g. as level 24 you receive 24 XP per cleaning.
 * You earn a specific amount of dollars increasing with your level, e.g. as level 24 you receive $2250 per clean.
 * You can collect extra resources for Time-limited events such as (past) the Thanksgiving and Christmas events (and so presumably future time-limited events).
 * As of v1.2 you can find blueprint pieces for the Wonder of the World quest by cleaning friends' buildings.
 * As of some version, the cost to purchase additional regions has significantly increased if you do not have enough friends, so you need to add friends to bring back down the expansion cost

No, because cleaning of structures is limited: To clean friends buildings first you have to add friends.
 * You can only clean 3 structures each 24 hours at one specific friend's island(s).  If you clean 3 on the first half of the island, you will have none to clean on the second half (if your friend's bridge is fixed)
 * You can only clean up to a maximum amount of structures every 24 hours, e.g. as level 24 you can only clean 51 structures every 24 hours.
 * You can only invite 20 friends in a day (ver 2.0.13)
 * Using the Level 24 example, cleaning 51 structures at $2250 income and 24 XP each gives you a total $114,750 income and 1224 XP per 24 hours for about 15mins of time visiting 17 friends, with no building cost, admin cost, energy cost or repair cost.

Hint: Until you complete the Mop Master Award, only clean buildings on the second island of any friend with a repaired bridge. By doing that the cleaing will count towards the general cleaning awards (130-136) and Mop Master (255). You will only get 3 cleaings per friend's island per day regardless of whether they are done on the first or second island.

Friends
To add friends, click on the Sociality button:

Click on Friends tab, click on Invite a Friend, and type in Friends' names (that you can get from Facebook and under game comments in app/play store) - note you must use their friends name, not their island name to add them. When they accept you you can then visit them and clean. You can post your "name" on facebook and in the games comments in app store, for others to add you as well and you can accept them in this tab. Until you have both invited and accepted you can not clean, just like you cannot clean any buildings from visiting islands in the Community tab.

Android friends and iPad friends are not compatible, so go to the appropriate Facebook or App/Market. ParadiseIslandAndroid Facebook page | ParadiseIslandHD for iPad Facebook page | Paradise Island for Kindle Fire Amazon page and although Paradise Island for other platforms are not yet updated to a version where you can add friends, for when they are, the relevant pages are here: (note, they are refreshing pages to visit without floods of page after page after page of rubbish: ParadiseIslandExotic for iPhone/iPod Facebook page | ParadiseIsland for Mac Facebook page Notes:

Limited additional features
From time to time there may be special benefits for visiting / cleaning friends islands. As of v2.0.14 these are:

1. If you visit friends' islands during a special event you will see one or sometimes two characters that you can collect additional resources from. You don't need to do any actual cleaning to receive these resources. Not every Special Event makes use of friends' islands.

2. For Helen's and Wonder of the World tasks you can receive a total of 15 Drawing pieces by cleaning at least 25 structures within 24 hours. (No Drawing pieces for the regular structures requiring Drawing pieces will be found here). Note that you cannot interact with the Wonder of the World building on a friend's island, no matter how it blinks, or has stars, or, or whatever.