Very relevant question! As a multifamily investor, I do work with a variety of different agents who also overlap territories/regions when I'm buying. It doesn't sound like this will be a popular answer, but I don't see anything wrong with it.
To me, this is about honesty, integrity, and your ability to build relationships. Don't get me wrong, it's not always the most comfortable place to be working with multiple realtors (if you focus on a particular region the community will overlap), but I would say you have to follow some ground rules to make it work. As several people have already suggested, you have to be upfront about not being exclusive. In addition, you should set ground rules so the people you work with know what to expect. For example, all my agents know that if two or more brokers bring me the same opportunity, I go with the person who got to me first - fair and square. They also know that if they get me a deal that closes, that's going to be theirs to sell when the time comes. There's a lot of value in being a straight shooter. The other thing that helps is just generally building a strong reputation in the community. Are you a closer? Do people like working with you? Are you always chipping away at commission? You can also help various relationships by referring new clients or rewarding some by listing properties with them that aren't tied to any particular agent. You can sometimes let your broker participate in an investment as a partner in lieu of commission, too.
The only caveat I'll add, is that you really have to be "active enough" to do this. Knowing that you're someone who is constantly buying, or that can close the big deals means brokers have a reason to want to work with you, even if you're not exclusive.
With all due respect to the real estate agents who've replied here, no single agent has access to every single deal (and in my very competitive market, a lot of deals are NOT on the MLS). And as much as I respect the value that brokers bring to the table, it's not like the agents are being exclusive to me as an investor either. The capable ones have several bigger investors for whom they are divvying up off-market product. Some agents who are also investors cherry pick the best deals for themselves, too. All I'm saying philosophically here, is that it just doesn't seem fair to be one-way exclusive.
Definitely DO NOT work with multiple agents behind the agents' backs, especially when you focus on one region. It may work for the short term, but you'll be found out eventually, and the hit to your reputation won't be worth it.
