Most of the illegal aliens in the US are from third world countries. They usually work jobs that pay poorly for wages that are even lower than poor Americans receive, at least at first.

I don't think you can come in and apply for a work visa while you are in the US. In order to hire you legally, a company must be able to prove there are no Americans available to do the work, and be willing to pay the fees to get you processed. It's always been a very slow process and is getting slower. I've heard that even tourist visas can take several months to process.

You might be able to work, but remember if you are caught and deported, you won't be allowed back in for a long time, even as a tourist.