That's true --- there are different kinds of illegals --- and they have different effects on this country. Many get visitor visas --- actually enter legally, but then they never leave. They may head right on over to the county hospital and give birth, they may stay with relatives or friends and mooch off them, they may get jobs and work illegally. Some others get shopping passes --- but really come back and forth every day to work --- the new laser visa seems to be catching more of these --- one of my neighbors had one and drove back and forth over the border very often --- cause he had a Mexican registered car and liked to go home often --- they took away his visa because they knew by all the times he came and lengths of stay that he must be working (of course he's back and still working but now without the car).
Then there are illegals who hook up with some organized crime ring that provides them whatever kind of documents like a stolen social security number or visas --- they might enter at a legal port --- they don't need to cross the desert if they have papers that allow them through customs. They get good jobs using their fraudulent papers. The ones coming through the desert illegally also are different types --- some are running drugs, some have criminal records and don't want to risk being detected at the bridges. Some are just unofficial guest workers --- they just want to work but don't want to commit another crime by committing fraud --- they're the ones more likely to be content raking someone's yard and mostly plan to go back home once they can.