I am late to this thread but just read it. I used to live in Manhattan, but now live in a NJ suburb. I have travelled to Queens and Brooklyn to see masseurs, but I am in the minority. If you want to come to NYC just to work, I think there are better cities that you would make more money that lack providers.
NYC is very expensive and competitive. NYC is not lacking providers, however good or bad they are. You would have to justify it by wanting to visit the city/meet people irregardless of your business. You might want to look into a swap where someone stays in your place in San Diego while you stay in their place in NYC, that is what some masseurs do. You will not want or be able to carry around a massage table to outcalls without having a car. Some subway stations don't have elevators and are very deep, for instance. Having a car would be too expensive for you, (parking is a nightmare and expensive, etc.). My suggestion is to rent one of the massage studios on 14th street (near the PATH train) every time you have an appointment (there are people who live in the city that do this, don't know the economics of it), and stay in Jersey City or somewhere cheaper, like a hostel or the Y, both uptown, if you are not picky.
Edit: I just read Simon's response to a poster about how to make traveling work. In Simon's case, given the level of service he wishes to provide and his business acumen, I would lean on not even bothering with NYC.