To add a different perspective to Lizzie's.
I work within the system and declare my earnings. After tax and business costs, I am probably on a similar wage to some of you on the forum, but better off than I was in a full-time civvie job at the bottom of the ladder. Bearing in mind though that except when I am on tour, I probably only do 2-3 outcall bookings a week, by choice.
Due to personal circumstances, I ended up starting again with nothing a few years ago. My part-time earnings from escorting first went on paying off a debt an ex-boyfriend landed me in, now it goes on basic things like replacing the furniture I was donated at the time with newer stuff, paying my rent, saving up to go back to University (already have a degree but it's pretty useless and I need a further qualification). I only really treat myself with things like shoes and clothes when it's my birthday or Christmas, I was brought up to value money and live quite frugally. The last thing I want to do is rely completely on a high volume wage, knowing that this kind of lifestyle might not be sustainable long term. I pay myself a wage and then the rest goes in savings towards medium and long term goals.
What escorting brings is the freedom of earning a graduate type wage, but in less time, so you are free to do other things - like volunteering, concentrating on your health etc.
I've met quite a few escorts who are similar, quite a few of us are part-timers.
When I tire from doing this, I will disappear into the civvie world and do a civvie job.
Probably a more boring answer than most people expect!