I have a balance in unearned rent of 50,000 (doesn't say if it's credit or debit)

Unearned rent represents two months rent received on December 1, 2008 for the renting of unused office space.

What would be the journal entry for this?

When you received the money on December 1, 2008 you should record:
Dr. Cash
Cr. Unearned revenues (Liability account)

On December 31 you should record the following entry to recognize the revenue earned from the rent:

Dr. Unearned revenue 25,000 (50000/2months)
Cr. Rent revenue 25,000