To answer your questions:
- How many 'illegal' aliens are there? (I've seen figures from 10-50mil)
The population varies since there is an ebb and flow accross the border. It is also a population size that has to be estimated from each census period because other means like DLs, voting records, etc. don't include this population. What you may be getting confused by is the total immigrant population which is roughly 16% - which gives us a number of roughly 50million immigrants.
Undocumented immigrants make up some subset of this with estimates ranging between 12-20million, But remember ALL population statistics are estimates.
.
- #2 How much are they costing us? (I read in an article they say locally, state and federally around $300 Billion).
Nope. Lets say that ALL immigrants were "illegal". That would mean that after collecting taxes from them EACH immigrant was costing us $6,000. That's just not realistic. In point of fact the GAO itself estimates that income tax compliance is in the same range as for the general population (70%-80%). And they pay property, and sales taxes as well.
In fact they contribute some $7 Billion in Social Security.
.
- #3 What part of 'illegal' makes it legal for them to even be here? (if illegal is ok, is it ok to break other laws? (i.e. they shouldn't be enforced either?))
Some laws don't make sense. Racist Jim Crow laws were ok to break by Rosa Parks et. al. And we know that the current immigration laws have their origins in racism and have been implemented in a racially discriminatory manner.
Now compare this to the millions of drivers who speed. We know that speeding is the primary contributor to fatal traffic accidents. Speeders cause a new 9/11 EVERY MONTH. So which laws are so sacred?
.
- #4 Are you here legally? (a lot of people that seem to think breaking the law is ok, are those breaking that law)
And you base this on ??? I'm a born US Citizen. Are you?