I would say it depends.
Many agents want to earn more commissions and you are providing them that opportunity. From one property the agent will get two commissions. Similar to having a client sell their home to buy another with that same agent. BUT better in your scenario because if the buyer were to have issues with financing or still looking at other properties, the agent would have a front row seat to that info.
If the list price is close to what you are wanting to pay, if it's a hot market, if it's an out of town or inexperienced agent or if you are experienced this can work in your favor. Some agents will immediately tell you they may offer a reduction of their commission or they will "make sure" your offer gets accepted.
Some agents are slime balls and can be incredibly deceptive. It would be hard for any person to remain neutral and "fair". Sometimes you will even see some agents cut throat to both parties and only care about getting their commission.
Essentially, you will become your own advocate. So make sure you have all correspondence in writing, double check all contracts before signing. If at any time you feel uncomfortable, contact local attorneys that specialize in real estate to see if you can ask questions. If you run into a serious problem, you can also contact the real estate board.
Sometimes dual agency can work beautifully and other times it can become a war. For anyone looking to do it, just be careful.