Brothels are illegal, but being an "out call escort" is not... so long as you know the work around.
One could easily be a "out-call escort", so long as you advertise that you are providing companionship for a night out. There is no mention of sex. However, if these two consenting adult happen to have sex, then that's great, they've hit it off. And if the person who used the escort decided to leave an extra tip, that's the "renter's" choice.
This is how they avoid prostitution charges. No mention of money is made after they meet face to face, and it's understood that if the escort choose not to have sex, then that's his/her perogative.
Personally, I'd love to run a legal brothel, and I'm in total agreement with the OP. There are three things people will always buy no matter what financial situtation they are in: Food, Sex, and way to escape.
However, instead of a brothel, one can legally open a swing club anywhere in the country. This would pose a different set of problems, but it's all on the up and up. And done very well, it can extremely profitable. I do adult shows at these places and they are always full!!
As to using filming porno as a front to prostitution, I've been making porno for about six years now (behind the camera, not in front) and I know that there are a whole bunch of religious groups who are trying to prove that all sex movies ARE prosititution, period. It's a stupid arguement by them but every few years, they try to prove it. So doing it that way is not advisable by me...