I am looking for a house to rent in Northwest Houston and am interested in hiring an agent. How much does that cost?

Sellers and Property Managers pay commissions on most deals.

I noticed you haven't closed out your question and wondered if you gained the proper understanding you were looking for. This is still a very common question/curiosity in regards to the use of a REALTOR when purchasing or renting a home. It is traditional in Texas Real Estate for a Property Owner to pay broker commissions to both his own "Listing Agent" and the "Buyer's Agent." In my opinion, this is the most logical way of doing things, because the Listing agent spends time, money, and resources to market and sell the home and the Buyer's Agent brings his client to the transaction to procure the sale. It is always the BEST idea to talk with your REALTOR and make sure you have a full understanding of how he is to be compensated for his work whether that be on the selling or buying side. Remember that you can always ask any questions, negotiate if you feel you should, and move on if you believe this agent is not right for you.

As a client looking to rent, your agent will highly likely be paid directly from the listing brokerage based on a pre-determined fee. You as the client, won't have to pay unless the rental property is not paying out a fee.

I am a Realtor, specifically specializing in Northwest Houston homes (Cyfair ISD, North Katy ISD{. To hire me you would need to sign a buyer tenant Rep agreemnt. You would owe me nothing, however the homeowner would pay thier agent; Thier agent would pay my Broker and I would receiive a spit of wha was paid to the broker. Homes are going very fast in this maket. Please call me between 11 and 1. you must for me by name. 281599 7600.

Realtor McKinley

A tenant's/buyer's agent in most cases receives their compensation from the lisitng broker who advertises what they will compensate a tenant's/buyer's broker in the MLS.
The Tenant/Buyer's Representation Agreement between the buyer/tenant and their Realtor stipulates how and by whom the broker will get paid.
Within the Realtor Code of Ethics in Article 9 of the Code it states that "Realtors, for the protection of all parties, shall assure whenever possible that all agreements related to real estate transactions are in writing in clear understandable language expressing the specific terms, conditions, obligations, and committments of the parties." Therefore it is acting in the highest ethical behavior for a Realtor to have all business dealings with their clients in writing.
The roles of both the buyer's agent and seller's agent are further explained in our Information About Brokerage Services. Here's the link.
http://www.trec.state.tx.us/pdf/contracts/op-k.pdf

I hope this helps you.

Yes and no...A real estate agent should get paid "through" the transaction meaning that the real estate agent signs an agreement to list the property. Part of that agreement is a commission amount and structure. So the agent that represents you the tenant or the buyer will get paid through that agreement that the listing agent signed. Meaning that you shouldn't have to pay your agent a fee as the buyer or tenant.