Answer:
Most economists argue that the economic impacts of immigration are usually positive and good for the overall economy, but one particular aspect where immigrants (as well as most minorities) tend to represent an excessive burden is welfare and social programs.
But if we include illegal immigrants into the equation, the percentage of immigrants seeking assistance programs will decrease dramatically since usually illegal immigrants do not qualify for this type of programs and even if they did, they are so afraid of deportation that they do not request government assistance and social services.