I actually am a manager, as well as an agent.
they are two different things. I keep seeing people saying managers are supposed to book you, but that is not normally the case.
quick rundown of they way it works. this will come from a label's perspective, but will include everything your manager should do.
ssuming a label thinks you are good enough to invest in:
the first thing a label does when it considers signing a band is how much the band/artist will tour. Will they tour if they are broke? Will they leave their jobs and girlfriends to do what it takes to make it in this shit. If the answer is yes, then the next thing they ask is who will book you. Many labels work with agents already, or have some lined up...but many good labels do not have agents that will pick up freshly signed bands (something I will do). Label owner hate doing anything like finding an agent for a band.
the manager aspect can come at different points. If you are lucky you will get one before you are signed. A manager does work to get your ass promoted in every way possible, but it takes money to make money. the less you have, the harder advertising will be. The goal of a manager is to get you signed, promoted through advertising, and a good agent.
some managers kill two birds with one stone (such as myself). Some managers are also agents, and wehn these types of managers approach a label they already have connections with, the label has less to worry about in signing them.
the myth i read on here "managers don't get paid unless you get signed." any manager that does this has no clue what they are doing. if you are spending time on promoting and helping a band gain recognition, you get paid. Time=money. a normally gets paid in this fashion 10-20% of everything you make. this includes merch, shows, signing bonus, and royalties. If a manager does not book you, he works out the deal with an agent for what his take will be. so if you sign a 20% deal and your manager finds you a better agent, he may do something like offer the agent 10% of your guarantees as compensation for him booking you. then the manager would still get 10% of the show money, and the agent would recieve the other 10%.
at a newbie level, it is very hard to book bands. much harder than dealing with large acts such as disturbed and Jay-z. realistic money you will make while touring for performances will range from $50-$300 on the usual. With a realistic average of about $125 a night until you get to the point where you are actually drawing people in the areas you are playing, then the money goes up.
as far as the whole selling out your hometown. yeah you will get approached by managers, but they are in many cases weak leeches. most good managers are not going to come to you, they already have something going on. if you start having a buzz about your groups in numerous areas, that carries a lot more weight.
i ahve seen many bands pull 400 to 500 heads in their homerown and when you put them on the road, not only can they not hack touring, their music doesn't ever really do well. difference is, in your hometown, a lot of your friends show up, and as well all know, friends will support a band even if they suck. when you are on the road, you get the truth.
I have been doing this for roughly 11 years for my bands, and in 1 year's time, I have gone from 0 signed bands to 4 nationals on my roster.
i knwo what it takes and i am open to anything, but as with labels i am very picky about anything i will work with.
i prefer hardcore scene bands, but will work with metal, and even good hip-hop.