You have 400K in assets, and 25K in investment income. This would interfere with fin aid at all but the most generous schools, not because of the investment income, but because of the 400K in assets.
Because he is luckily a US citizen, if he could get into a school that is generous with financial and/or merit aid, he could probably swing it without help from you. He is in a MUCH better position than international students without US citizenship.
He has very nice grades and SAT, but this probably won’t be enough to get him into a T20 school unless he has some very interesting EC with extraordinarily high achievement.
He has several options. One, take a gap year and move to the US to a state with a low cost of living, and a flagship state U with a good comp sci department. It needs to be a state that gives in-state residence for community college after 6 months, and in-state for flagship state U after 12 months. He works many hours/wk in the best paying job he can get (I’m talking a full time and a part time, probably 60 hrs/wk) while he gets in-state residence. Meanwhile, he takes as many CLEP exams as possible to CLEP out of as many gen ed classes as possible, for free. Take a look at modernstates.org. He applies for fin aid for January, goes to a community college with a guaranteed transfer to the flagship state U, at a very fast clip (community college in the US is absurdly easy, so he could take possibly 6-7 classes at a time). He can get $5500/yr in student loans from the federal gov’t without any financial need, and probably more, since your income and assets are relatively low, by US standards. He also would probably get a full tuition scholarship from the community college, since he’s such a good student. He then transfers to the flagship state U after he gets his community college degree - he might be able to transfer with his associate’s degree by the next September, after only a spring and summer semester at the community college, maybe would need as much as 3-4 semesters, depending upon how much CLEP credit he can get. If his grades continue to be excellent, he would likely be given a full tuition scholarship at the flagship state U. Graduates with his Comp Sci degree after two years there, gets a good job, employer pays for his master’s degree. Utah is one state where this is feasible, but there are many others.
Option 2. He applies now to good schools in the US that offer full rides, or at least full tuition, to excellent students, as he is. This is an option for him, because he is a US citizen. Honestly, a degree in Comp Sci from almost anywhere gets you many good job offers in the US, and after the first job, no one cares where your degree was from. Plus he can get a master’s from someplace good, and then he has a famous degree, too.
Option 3. He joins the National Guard. It will usually pay for tuition at any state school in the state where he is in the National Guard, plus give him some living expense money. He’d have one full summer in it, then one or two weekends a month and two weeks every summer, plus he’d be liable for being called up to serve further.
So, because he is a US citizen, it is really very possible for him to go to school in the US. If I were him, I’d explore and shoot for the full ride at a lesser school option, because he would have little to no debt, and not have service obligations. But the others are there as backup.