she might accept your word for your pal, esp if you have seen her more than once.  If you have not seen her, it's doubtful that she would, IMHO, since she does not know you from Adam's housecat.  Either way, there are no guarantees, all you can do is ask.  I would suggest you have your friend join one of the verification sites as well.

Swim

I am not a provider so I can't speak for them, and I am sure a few will chime in on this thread eventually. However, common sense tells me that the overwhelming majority of ladies will not take a refernece for some new client they never saw, from another client they never saw. On the other hand if you have a "regular" gal or someone you have seen two or more times, and you feel comfortable with her, and her with you, she may take a referral. All you can do is ask. (This does seem like it is along the lines of your thinking anyway, according to your OP).

On the other hand, he could start off like any other newbie. Look for newbie friendly ladies, be willing to give up some personal info, and perhaps join one of the verification sites. Good luck to you and your friend.

I have given references to providers who know me well for other hobbyists whom I have also gotten to know well.

I have referred three separate providers to a small circle of friends/hobbyists who I correspond with on TER and other places.

These girls trust me to do some basic vetting, but I always tell the hobbyists that they may screen further.