An agency will take almost half of your earnings but you will not have to pay for your advertising, website, accommodations for incall, furniture, bed linen and towels, body guard, lawyer, driver, etc.
In any event if you are independent or a part of an agency your main goal is to build a loyal repeated clientele.
Think of how many men have fallen in love with you before you decided to become an escort, if the answer is positive you are in the right industry!
If you are independent you have to be highly organized, it is rather difficult to be busy with a client and not to miss a phone call, (messages left over on a voice mail seldom work), you will need to learn how to hear bad from good, how not to go on empty or dangerous calls, you will need to drive at night to unknown places where the street numbers are invisible with no parking, or expensive parking at hotels or take a driver or a taxi, that will automatically drop down you call rate significantly.
It is also rather dangerous, no one will know where you have gone to, you are much safer with the agency. If you choose to be independent take care of your safety, find a friend (female is better, then you would exchange the favor) who will know where you are going to and who is coming to see you.
As far as an incall is concerned, safety is also first and foremost, you will have to decide if you would like to work at home or you will need a different place, it depends on security system in your building, on the concierge, on the neighbors how close you are to the elevator, who lives under you and will hear you high heels on the floor if you do not have a rug, you will have to think about your neighbors when you switch on the music at night, it also depends on the area you live in (far or close to main highways, easy to find address, etc), ethnicity of people living around, etc
If you are independent you will also need to advertise yourself In different advertising directories