All wise words, I feel, although possibly distracting us from the original question! Thank you Forbes for clearing up a number of details - I appreciate that you have a very detailed knowledge of screen industry work in particular, and it was my assumption that most Walk - On Agencies charge a basic book fee. Thank you for confirming that. Any reputable actors' agent does not.
Charges are not at all uncommon, I didn't think, for even highly reputable walk - on agencies, who will also take commission (as I think Clive indicates) - and while Alan is no doubt right to stress that in accordance with Equity guidelines, no agency should be joined which is charging an upfront fee, I feel that this issue becomes clouded in respect to walk - on agencies, where, after all, the charging of fees is, as Forbes says, the legal norm, rather than the exception.
'Guys and Dolls' appear, on my cursory inspection, to be as reputable a walk - on agency as any, but I feel that charging consistently every month is pretty extortionate - a one off fee is not at stake here. As Clive suggests, there is never any guarantee with a walk - on agency that they will make you any money at all (or, at least, that you will make much profit after charges), and I am with Forbes on this one, the type of money you can make is strictly supplemental. But there are many extras who work extremely regularly, and consistently, and enjoy the work.
I understand Forbes's argument that this is not a dispute for these forums, but it seems to me that there is simply confusion here - with a regular actor searching for representation, and being offered some walk - on work without recognising the agency for what it is. This *is* a question for these forums, if only so we can get the distinction right. Walk - on work is strictly for you if you have an especial hankering for it, or you want to earn yourself a bit of 'pin money'; it cannot advance your career as an actor, and, as has been said, most who do it are hobbyists and enthusiasts. A point I was making earlier is that these distinctions may not have been made clear in the initial search for representation, because agencies of this sort will be happy to take you onto the books if you offer yourself, and many actors desperate for any sort of representation will willingly sign up without knowing that this type of agency cannot adavnce their career at all.
I hope that has cleared some of the confusions up!