Kingleds is right - I know a number of consultants and they are not making enough to consider giving up full-time employment.
The amount of the takings that you keep depends on the size of your group. I don't know the exact figures, but for instance if you had 50 members you would be able to keep a higher percentage than if you had 20. You have to have a large group to keep as much as 50%. I know from my own group that a lot of members see the money going into the cash box and think that it all goes to the consultant, but it doesn't!
You have to pay for everything - hire of the venue, all your stationery, all the things like stickers and slimmer of the week certificates, publicity material, advertising, posters, leaflets, etc. You have to pay to register under the Data Protection Act (because you will be keeping members' details on your computer).
It is also a lot of work. Meetings must be prepared for, rooms and equipment set up, members contacted (and they contact you, not always at convenient times!), and you would have to attend regional meetings.
I am not trying to put you off (really!) but you would need to look into things very carefully indeed before making a decision.