Agents earn by getting you work - i.e. they get paid if you get paid.
In my own experience, agents that ask for £££ to 'join' are probably making their money by getting people to 'join' - and not necessarily by getting any work.
This recruiting method means that it is in their interest to have as many 'join' as possible. Therefore, there will be many competeing people on their books and thus the liklihood of an individual getting any work, is rather slim.
You'd probably find it more rewarding to go to a casting or extra's agency. As for modelling in itself - this is a very difficult industry to earn from indeed. Do you have a portfolio?
As James says, our model/photogarpher networking community will be 'reborn' soon and I think it will be a great way for everyone to develop their pinup portfolios and such. 'tis all very exciting...
