Is there a site for mobile numbers some guy who owned a Agency told me you can check mobile numbers online, though wasn't sure if he was making it up as he doesnt screen clients.
There was (I don't know if it is still up and running) but it was woefully out of date and most people I know understandably had their details removed from it as soon they heard of it's existance. Why would you want to check mobile numbers anyway? If you are sending women on outcalls then it's normally landline/electoral roll for home visits or the booking details for hotels, same as the rest of us.
If you are only taking 20% (which is indeed a very competitive rate, and I assume it is because you are not providing transport) then you are going to need to be very busy to cover your start up costs, website, advertising, photographs and so on. Plus, as agency bookings are supposedly down everywhere and reputation is incredibly important in this industry, do you envisage really being busy enough to cover these costs as you will need to charge competitive rates to get bookings? And have you thought about what you will do if you're not busy enough?
I'm not trying to put you off but as Cassie said, rightly or wrongly I am going on other posts you have made and I honestly don't think you have thought about what you are up against. Just because some other people (gender is irrelevant) have done something badly does not automatically mean you will do it well - I used to work at an animal rescue but that does not make me a vet. Things always look easier on the surface and this is no exception, which is why every man, his dog and his silver haired mother is starting up an escort agency.
I would do some serious research if you do decide to go ahead, and as for the legalities somebody mentioned, that's the easy part. There aren't any, and you need to think about that as well.