This is a very stereotypical, maybe even racist way to look at this situation. You seem to come off as if the members of the caravan, as well as Latino/a immigrants in general, are of high risk and pose as a potential danger for this country's security. That simply isn't true. These are people who are fleeing their home countries of Guatemala and Honduras due to persecution and extreme poverty. All they want is a better quality of life, not to cause harm, like conservatives think. Yes, drug cartels and violent gangs do exist, but the amount of people who "illegally immigrate" who are coming for the sole purpose of bringing in drugs and recruiting gang members is miniscule enough that it's irrelevant. It's a racist stereotype (perpetuated and encouraged by Trump) that most Latinos are criminals, when in fact that is as far from true as you can get.
I put "illegally immigrate" in quotes as I am a firm believer in the principle of "no human is illegal on stolen island". 400 years ago white people "illegally immigrated" to the Americas to seek a better life and few people seem to care, but when brown people start doing the same, it suddenly becomes a national crisis. And don't say it was because "America wasn't civilized back then", because it certainly was. Native American cultures nationwide had set up organized governments and were more advanced than most of us think. Iroquois, as an example. There are over 600,000 known illegal immigrants fro Europe in America but no one ever talks about that being problematic. Whether we want to admit it or not, this is an issue of xenophobia and racism. White people are simply scared of those who do not look or act like they do living in America, this supposed melting pot. America, a country that is not only tremendously wealthy, developed safe haven, but one that is compassionate and accepting. We should feel sympathetic for the "illegals" and provide them the means to prosper here, rather than alienate them and see them as the problem. These people "illegally immigrate" for a reason, and it's not because they're criminals. Getting full citizenship in Americas takes multiple years. For many, it's a life or death situation; they can't afford to wait all this time to become granted as "actual Americans". And that's totally acceptable.
As for paying this mass immigration, it can totally be done. Not under a capitalist, nationalist Trump government, however. Yes, the majority of these "illegals" will need government services, just as food stamps, rent assistance, and other forms of welfare. That is also totally acceptable. The government should also provide job training, childcare, contraception, free health care (covering mental health conditions and pre-existing conditions as well), and free university to them. How can this be done. Simple. Tax the wealthy and large conglomerate corporations more. We all need to pitch in. No, not everyone will be enthusiastic about their taxes going up (albeit by a very small amount), but it's for a good cause. We're helping people. At the end of the day, citizenship is just a certificate, not a way to judge who is valid and who isn't.
America can not truly progress if we continue to have the regressive mindset that brown "illegal" immigrants are the problem. Xenophobia is the problem. Whether they have their citizenship or not, the extreme majority are productive members of society. Bigotry accomplishes nothing. Trump, for example, threatening to close the US border and cut off food aid with Honduras if the caravan isn't stopped is a prime example of regressive, xenophobic bigotry. It's no small issue, and in fact, it should be seen as a breach of human rights. He is putting lives on the line, of innocent people. And those who think, "not Americans, so not our problem", only cause more insult to the injury.
