Now, Trump has had to back-peddle a bit on this single-payer healthcare stance since he's trying to appeal to Republicans. Still, he's been pretty clear that it is what he still wants, if only to make US businesses more competitive since they wouldn't have to pay for their employees coverage.
On illegal immigration and the concept of open boarders, we all know Trump is very much against it and wants a wall to keep people out in order to reduce crime and the various costs associated with all the people coming in through Mexico.
Fewer people seem to know Sanders' position. When asked about open boarders as a way to reduce global poverty:
"It would make everybody in America poorer--you're doing away with the concept of a nation state.
"What right-wing people in this country would love is an open-border policy. Bring in all kinds of people, work for $2 or $3 an hour, that would be great for them. I don't believe in that. I think we have to raise wages in this country, I think we have to do everything we can to create millions of jobs.
"You know what youth unemployment is in the United States of America today? You think we should open the borders and bring in a lot of low-wage workers, or do you think maybe we should try to get jobs for those kids?"
It's well established in the US that Big Business enjoys illegal immigration since they can use the deluge of cheap labour to push down the wages they pay. This is why there has been almost no effort by either party to clamp down on it. Now, both men have different reasons and methods for doing it but both Sanders and Trump want to deal with this situation.
While Trump wants an actual wall to keep illegals out and intends to round up and deport the eleven million currently here, Sanders would prefer amnesty for those already in the US. He also doesn't seem to have formulated much of a plan to stop those coming over illegally but as a socialist whose main constituency is lower-wage workers, he is clear that something needs to be done to prevent them from taking US jobs and pushing down wages.
On the topic of H1B visas, that is, temporary visas granted to foreigners with skills in "short supply" who temporarily reside and work in the US, both candidates are completely against it. In reality, these visas are asked for by major technology firms like Microsoft and Facebook so that they can replace their higher-paid staff with much cheaper foreigners who never actually get to become Americans and have to leave if they lose their job. In many cases, American workers are forced to train their lower-paid replacement in exchange for their severance, a practice that must be blindingly rage-inducing and makes a joke out of the idea the skills are actually in short supply. You don't fire someone whose skills you need and are in short supply.