I have over the years asked a lot of providers how they got started in the business. By far the most common answer is that they knew someone else doing it and were attracted by the extra, tax free income. Some got to the point where they could leave a job they didn't like very much.
The second most common answer was that they were propositioned a number of times and finally gave in, and it grew from there.
The third most common was that they started as porn stars, but that income for most is not enough to survive on, and added escorting.
Of those who were recent immigrants, many of them seemed to need the money to survive.