The best way is to have your real estate agent contact the listing agent to see what sort of listing agreement they have with the owner. They will disclose whether or not it is exclusive.
Don't get too hung up on that. Try to concentrate on whether a home is a good value for you and make your offer. There are good and bad FSBO, wholesale, retail, and REO deals. Just because you get something FSBO doesn't mean it is a good deal.... more