If you're only loading data to access it once, then yes, but it almost never is the case - some specific programs might do it, but OS definitely caches pretty much everything it can in RAM for subsequent access - Linux, for example, fills unused RAM with cache
That was my first thought as well. Assuming a large enough amount of immigrants, they could be overwhelming both the welfare system and the job market. A sufficiently large group of additional people would overwhelm every system, and depending on the preexisting conditions, that group might not need to be all that big