Ask a Realtor for advice and comparisons. There are some who specialize in rentals.
If you want to get a quick and pretty good estimate, you might want to try this website:
You can generally go by the going rate in the area.
you can check rental rates off of craigslist, zilpy, zillow, and here on trulia.
Generally you can go by square foot of the home and number of bedrooms.
Harold Sharpe - Broker
So Cal Homes Realty
California Department of Real Estate License # 01312992
Your agent can help with this. One thing to keep your eye on is the commission - generally here in NJ it is equal to one month's rent and is usually split between the listing agent and the renting agent. The listing should specify who pays, ie, tenant, landlord or a split between the two. If tenant and/or split, you may be able to negotiate further if your lease is otherwise strong.
Good luck to you,
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