This is a complex subject. I reject the standard positions of both pro and anti immigration groups. I view the pro immigration groups as engaging in unprincipled pandering to minorities and immigrants in the name of simply snagging votes (I.E. increasing political power). I reject the notion of subsidized immigrantation. On the other hand, I think, besides the racist elements, the anti-immigration crowd can be summed up in one word: protectionism. That is, these people's motivation is to disemploy immigrants and certain groups within society while getting government-mandated jobs themselves.
This issue is no longer about immigration or even illegal immigration anymore. It's all about economics: using government to "protect" certain groups at the expense of others. It goes both ways too. Anti-immigration people seem to want to recieve special protection by illegalizing the jobs of immigrants (effectively stifling competition over labor). Pro-immigration people seem to want to give immigrants special protection by subsidizing the jobs of immigrations, which in turn stifles competition over labor as well. Both roads (subsidization and prohibition) lead to disaster.
When you subsidize something, you get more of it. Not only that, but you pass the cost onto someone else. Hence, subsidizing immigration functions as a (misleading and all around bad) incentive for people to immigrate. It further imposes a burden on those who already are paying taxes into the system to pay for the spending necessary to fund the subsidization. Consequentially, in the case of subsidized immigration at least, some of the claims of the anti-immigration crowd with respect to the economic costs of immigration are at least superficially true (it's just that it only applies to SUBSIDIZED immigration). However, it gets distorted and exaggerated easily.
When you prohibit something, in the short-term you might get less of it. But in time it is inevitable that a black market arises despite this limit on supply (example: we have drug and prostitution illegalization, yet we have a black market in these areas). Thus, to overtly prohibit immigration will do nothing to stop people from simply immigrating anyways, just like prohibiting drugs does nothing to stop people from buying, selling and using drugs. If you illegalize the hiring of "illegals", you will simply create a black market for those jobs, and thus those jobs will continue to exist.
From both an ethical and economic point of view, I should be able to invite whoever I please into my home, including immigrants. I should also be able to hire whoever I want so long as it is a voluntary contract between me and the employee, even if they are an immigrant. In this respect, my position can easily be misinterpreted as "total open borders" by anti-immigration people (and it has been misinterpreted as "exploiting workers" by pro-immigration people). But there are limitations on this. Immigrants would completely be in the wrong if they are trespassing on my private property without my permission, and I have every right to have them expelled. Likewise, to use a more extreme scenario, they have no "right" to homestead on property that is already owned, against the owner's consent. I also oppose all welfare benefits for immigrants, but that's not because they are immigrants: I oppose all welfare period.
Outside of that - if you want to come to America and buy property, get a job, etc., I say the more power to you. If you want to come to America to flee 2 dollar an hour wages in Mexico to get payed 10 dollars an hour in America, not only are you making a rational choice (no matter how much people rant about "exploitation of cheap labor"), but you're helping improve our economy. Comparatively speaking, immigrants who are being payed such wages in America are not being exploited at all. Compared to their previous situation across the border, it is a massive increase in economic oppurtunity (by much more than a margin of 200%) and overall well-being. If I lived under the conditions that many of such people are fleeing, I'd be dieing to come to America too, and a 10 dollar an hour job working as a maid at a hotel or what have you would be paradise on earth.
When I take a road trip across America, a reoccuring thought enters my mind: There is an endless abundance of unused land or land for sale in America. America is by no means overpopulated. Not even close. We might have some densely packed cities, but these cities are like islands in a sea of either (1) rural townsips or (2) unused land. We have vast stretches of land in Texas being completely unused that could be developed. America is by no means "over-developed". It is underdeveloped when one looks at all of the unused land in such a large national territory. If immigrants wish to buy such land, I encourage it. There are plenty of untapped resources around here.
Of course, there is a problem standing in the way of the use of this land: government ownership of land. Not only government ownership of land, but government ownership of land that is currently being put to no use at all, not even stewarded in any way. I say privatize it and develope it. And who, pray tell, has the most to gain from such developement? Why, immigrants! The government is simply blocking the use of perfectly good resources that could be used, among other things, to provide developement for immigrating people.