Greeting from Softhunters technology pvt ltd.
As i have seen all your requirements
1. Back End: User accounts, including, administrator, merchant / agent user, regular user, and property owner
2. Online property rental period management ( dates to be rented out )
3. Listing of available properties; including property features such as dryer, washer, etc,
4. Multilingual switch, Mandarin, English, Japanese ( including back end panel )
5. Paypal payment integration
After lookout of all your features ,i would like to tell you that We have Professional developer for these particular features .
i will wait for your reply for further discussion.