With that being said the manager and artist will normally negotiate between 5% - 25% of either the gross (before taxes and expenses) or net (after taxes and expenses) revenue to be paid from the artists income to the music manager. It's always best to have a written music business contract between the music manager and recording artist.
The promotions side various depending on if the promoter is working a particular project in some instances they may be paid a set amount for the project for a certain period of time. In other situations the promoter may be paid a monthly retainer to execute certain marketing and promotional duties. The manager and promoter or two separate job descriptions that may overlap from time to time.
TRUTH TIME - If you don't have any money, get a job (9 to 5), make money online, save your money and cautiously invest it in marketing that will give you the highest return. Humbly, I suggest using the Internet by creating a website(s), blogs and a number of other social media profiles. It will be very difficult to get your name in the market place without commitment and money.
When the artist has the right attitude, constantly works to perfect their craft and performs every chance they get the right manager will find that artist. If no, manager is approaching you, you aren't creating the best music possible and performing that music frequently. When people like what they hear they will approach you. This isn't what most artist want to hear, yet this truth will allow you to know if you're ready to advance your career or go back to school and become a doctor, lawyer or accountant which are always in demand.
Make sure you have a written music business contract. You'll also want to hire a music attorney.