Although there could be Stockholm syndrome.

Cos, as you know, if any girl needs help, she's gotta help others  to help her.

1) No review history.  And even if there are some good reviews, as other posts in other recent threads attest, you can't always be sure.  But usually this is the best indicator you have.  The more good reviews, the better.  Ladies that participate on the boards are usually a good indicator as well.     2) No rates posted.  In most of the ads there by ladies I've known over the years, rates are usually included.  Enough so that I take this into consideration when viewing that site.  3) Fake pics.  There are times where you will see pics of erotic models or pornstars that will lead you to conclude right off the bat that the ad is bogus.  There was also a now defunct agency that was infamous for this a few years back.  If in doubt, TinEye and other reverse image search engines are resources that may help.   4) Seeing the same phone number in more than one ad.  Happens more often than you might think, and many hobbyists are too dazzled by the pics to notice.  5) Something about the ad just doesn't seem right.  This is usually something intangible, where your intuition just tells you to be cautious.  

Note that none of the above are guaranteed to indicate rip-offs, B&S, or other unpleasant experiences are likely, but they are signals that need to be considered in your selection process.  

All  that being said, Eros is not a bad sight, and if used in conjunction with reading reviews and doing your homework, can lead to some most excellent experiences.  At the end of the day, though, it's always caveat emptor in the hobby.  If your gut tells you something isn't right, you'll usually be correct.