Interesting and complex topic. You should have no trouble finding resources.
I'll suggest an alternative, that of school and municipal services funding relative to the resource burden. School districts are not allowed to turn away any child presented to them, particularly special ed districts. This is regardless of whether the child actually lives in district or there are funds for the child's education. What is exasperating to many already underfunded special school districts is when a child from a family of undocumented workers is presented, and that child has severe disabilities. These disabilities require the attention of specialists, which are costly, and may require the school to hire an interpreter to facilitate communication with the parents, which is also costly. Moreover, where illegal immigrants are forbidden from owning land, they rent and therefore contribute nothing to property taxes, which are often the major source of funds for the special school district (note that an apartment owner pays property taxes regardless of whether an apartment is vacant or occupied). Moreover, where state income taxes fund education, an undocumented worker cannot pay income taxes (it is impossible without some form of identification). This indicates a use of services without payment for them.
A second thought may be that of identity theft. In order to work legally, one must have either a SSN or an alien identification number in order to file the appropriate tax papers (W-2, etc) and have wage taxes withheld. In order to obtain legal jobs (ie, not cash under the table) many have resorted to stealing identity numbers from residents and citizens and using them for work purposes. This distorts and may tarnish a citizen's work record and damage their credit rating. There is anecdotal evidence of persons being denied jobs with a company because records indicate that they had previously been fired from another branch of the same company in another state, where that previous firing was of an illegal immigrant posing as the applicant.
I do need to point out a few things:
* There is a difference between unemployment and loss of wages. Unemployment means that the American lost or was unable to find employment, while loss of wages means that wages are lower than they otherwise would be in the absence of downward wage pressure from illegal immigration. The 40% to 50% statistic seems much higher than studies I read, so I question it. While the presence of illegal immigration is often cited as a factor in wage depression, it is an increasing reliance upon information technology that is cited for an elimination of many types of low-wage positions as well as factory positions. You'll have an easier time proving the point of wage depression than unemployment, and you'd do well to look at wages in cities of similar size with disparate estimated levels of illegal immigration; ie, if wages in Sacramento zip codes with high estimated levels of undocumented persons are 30% than wages for the same jobs in Seattle zip codes then that suggests a discrepancy may be due to illegal immigration.
*Your point on health care is a non-sequitur (does not follow logically). While it is true that more than half the immigration is illegal (estimated, anyway, since there is no way to track for sure), illegal immigrants are not thought to utilized more health care than citizens as a group. For one, they risk exposure and capture. For another, studies have tracked a much larger impact on health care costs being due to longer life expectancies and the ability to treat (at a much higher cost) far more serious illnesses and injuries. To draw a parrallel, much of the cost of treating Iraq and Afghanistan vets stems from medicine being able to save the lives of many whose injuries would have been fatal 10 years ago. You'd have a very difficult time trying to prove rising health care costs are due to illegal immigration.