It seems that most have approached your question with the same perspective-that you are unsure or perhaps not in control. I'm thinking that you may be asking because you like the Listing Agent on the home you are buying, that they are professional, have presented the Seller's home well, and seems like they are flexible in working with your contingent contract. You may have been so impressed with this agent's performance, that you see this choice as the best course of action in getting where you need to go.
The listing agent of the home you want to buy will already know your financial condition. They would not take the house off the market for a contingent contract unless you shared everything with them. Of course, they will be motivated to sell your home, so you can buy their listing. That doesn't mean that the agent will put their own interests first, give your house away, or talk you into anything that you don't want to do. If you have any doubt, interview more agents.
I would insist that everyone use a Buyer's Agent to assist them in their purchase, however not every Buyer's Agent makes a great Listing Agent. and vice versa. When hiring any professional, interview, ask questions, get references AND a guarantee that if their service isn't what they promised, you may cancel your agreement with 24 hours notice.
I know this is an old question, however it's a good one. Good luck in your real estate deals!
RE/MAX Realty Group