After much discussion, my partner and I thought it might be fun to experiment with a threesome. He would prefer to hire an escort for this to avoid complications. I'm happy to try it but we are both worried about the legal implications and unsure what to expect. I don't know any women who have done this with a partner or even alone. I enjoy new sexual experiences and think it could be a lot of fun, but I'm worried as I don't know how it will feel to sleep with someone who may not actually desire me. It's important to me if we do this that it's not with a woman who is being forced into prostitution or exploited. But I have no idea if there is any way to know that.
Sounds like your boyfriend wants to hire an escort to avoid any emotional involvement. But a bit of emotional involvement would set you more at ease because you want to know the other woman genuinely desires you. The two of you might do better at a swingers' party or convention, where you can meet women who are more experienced with threesomes and definitely into other women. Most people in the swingers' lifestyle have good boundaries about sex. The whole point of swinging is to be able to enjoy sex outside of a primary relationship without jeopardizing that partnership.
Prostitution is illegal, but I can't see how you would get into trouble for hiring an escort. You aren't going to tell, and neither is she, so I think you are safe in that regard. When you call the agency, you can explain that you are looking for a date for a couple. A woman who is not interested in bisexuality won't take that assignment. Most escort services have a policy that they do not provide sex. The fee that you pay is only for so many hours of the escort's companionship. Theoretically, you are supposed to take her out to dinner, the opera, whatever, and be amused by her mere presence. In real life, clients and escorts sometimes negotiate an additional fee for sex. That way, the agency is not legally responsible for an act of prostitution.
This may seem odd to you, but bisexual and lesbian women do become escorts. To them, men are for business and women are for fun. It can be a rare pleasure for a sex worker like this to introduce another woman to the pleasures of the female form. I think you'll be able to tell if there is chemistry when you meet the escort. If you don't find her attractive or you are unable to relax and believe that she is okay about being there, you shouldn't go through with the sexual part of the date.
While some sex workers are the victims of trafficking, others may be single mothers, graduate students, or independent-minded individuals who like the open-ended schedule and potentially high pay in this job. A client who pays the agreed-upon fee and is polite, clean, and clear about what they want is a bonus. You'll probably be her favorite date ever.