What you are talking about, and correctly trying to avoid, is dual agency. This takes place when the listing agency attempts to represent both sides of a transaction.
As a buyer, there is NO EARTHLY REASON for you to accept or consent to dual agency. Simply tell any agent you come into contact with that you will not consent to dual agency, do not want dual agency, and will have your own agent contact them if you are interested in pursuing the property.
A good listing agent will be HAPPY to agree to this. But the listing agent's happiness is irrelevant. You should ALWAYS have your own representation.
Here are some things you can expect from a good buyer's agent:
1) Your buyer's agent has the same goal as you: obtaining the property for the lowest possible price.
2) A good buyer's agent will look for trouble with the property that would cause you to lower your offer. These problems include physical problems, functional problems, and locational problems. After inspecting tens of thousands of properties, I will spot things you will miss. Things you will DEFINITELY want to know about before deciding on the correct offering price.
3) A good buyer's agent will look for trouble with the seller that would cause you to lower your offer. Bankruptcy, foreclosure, divorce, impending relocation, frustration with past deals falling through, the list goes on. The listing agent will NEVER tell you any of this. You need a good buyer's agent to cut through the BS and learn the truth about the seller's motivation.
4) A good buyers agent will help you explore the market effectively and waste as little time as possible looking at houses that won't make the cut. This means handling all the logistics of gaining access, scheduling showings, etc. In short, making it easy and fun to inspect your next home!
5) Transaction management. Once you finally find your home and get an offer accepted, there are a million traps and pitfalls to avoid prior to the closing. A good buyer's agent will be indispensable during this process. Analyzing the home inspection, dealing with the attorneys, handling the appraiser, dealing with the various trades if repair estimates become necessary, etc, etc.
And guess what this costs you? Zilch. The buyer's agent is paid out of the commission already agreed to by the seller. That's why dual agency is such a trap to be avoided. For no extra cost, you get your own representation. If you fail to get your own buyer's agent, what happens? The listing agent gets 2 commissions and you get ZERO representation. Does that sound like a terrible deal for you the buyer? Of course it does!
So to avoid this, retain your own agent before actively inspecting homes for purchase. You DO NOT have to sign anything! Simply interview agents and pick one who is experienced, highly qualified, and friendly!
ONE IMPORTANT CAVEAT: NEW CONSTRUCTION
It is vitally important to realize that special rules apply for new subdivisions. Most builders will pay your buyer's agent's commission. BUT ONLY IF YOUR AGENT SIGNS YOU IN ON THE FIRST VISIT! If you walk into a builder's sales office alone, you have pretty much lost your right to your own agent. The builders advertise and spend a lot of money on marketing. They will NOT pay a buyer's agent after the fact if you walk into their sales office alone.
So again we come to the same correct procedure as before. Retain your own agent FIRST before you do any physical shopping. It costs nothing. There is no obligation. You do NOT have to sign anything. You can dump your buyer's agent at any time if you feel they are not doing their job.
As far as what to look for in a buyer's agent:
1) Experience as a Realtor. You want someone who knows the ropes and will actually contribute to the deal by saving you time, money, and hassles.
2) A related skill is also good: A Realtor who also has experience as a home inspector, appraiser, or mortgage professional brings more to the table than someone who has only sold. For example, I've been an appraiser for 20+ years.
3) Full time Realtor: You do not want a part-timer or dabbler. You want someone who is in the trenches each and every day.
If you have any further questions, do not hesitate to ask on this forum or contact me via my profile.
And for further info on the pitfalls of dual agency, just Google "real estate dual agency" and learn the ropes!