If you are looking to determine the market price of a property you have for lease, or you are looking to lease a place yourself, you should do a bit of legwork or hire someone to do it for you. Look at several places near the property to get an idea of rents, look online at sources such as latimes.com or westsiderentals.com (westside rentals is free for landlords and has an online tool to help "comp" your property, or hire an agent to help. You also might want to check out rentometer.com, which is fun and informative, although it doesn't quite have the zillion points of data to really nail down a price.
This is important because once you start looking for a tenant/buyer, the clock is ticking. Asking too much rent causes you to waste your time showing the property and your money paying for ads. In addition you'll want to snare that perfect tenant/buyer by having your property rents at the right level beginning with your first showing.
Fill your properties more quickly
A rent survey is an analysis of what properties similar to yours are renting for. A good rent survey allows you to fill your properties more quickly since you won't be asking for too much rent. If you've agreed to pay too high of a monthly payment to the seller, the rent survey gives you the information you need to go back and renegotiate the payment with the seller.
The easiest and most direct way to do a rent survey is to simply walk down the street and start knocking on doors. This gives you a chance to look closely at the neighborhood as you walk through it. Ask the people you meet the following question: I was thinking of renting in this neighborhood. Do you by chance know how much other people are paying in rent for a ___-bedroom house (or condo/townhouse) around here?
Notice that you ask them if they know what other people are paying in rent. We've found this is a less intrusive question than asking them what they are paying in rent.