Take a look at other rentals in the area and if you think the increase will bring the rent to above-market value you can always negotiate the increase down; losing a tenant is costly to a landlord so you may have some success.
Yes, if you lease contract is up. And you should read what your contract says. If you sign a one-year lease agreement, the landlord has to honor the terms of the contract. If you have month to month lease agreement, at the end of the month the landlord has the right to change the terms and rise your rent. If you are willing to sign a longer contract you may be able to convince him to not rise the rent. If I can help you by providing you a list of homes leased in the past few months let me know. So you will know if you are paying a fair price.