How Many Credits Freshmen Year Should I Take?

Hi!
I would like some advice. I read through some threads, but I guess I would like some opinions from college students about my own classes.
I am starting my freshmen year in the fall, and I am debating on whether or not to take 14 credits or 18 credits. I already have some understanding of classes (I took 8 credits per semester senior year on top of AP/Honors/Advanced Classes).

The classes I plan on taking first semester are:

Writing Techniques (3 credits)
Natural Science Lab (3 Credit Hour)
Spanish 101 (4 Credits)
Macroeconomics (3 credits)
Calculus I (4 credits)

I was undecided on whether or not take Calculus 1 this semester. I took AP Calculus AB exam junior year (got a 5) and the Calculus BC exam (waiting for the score back) so I know the class won’t be too difficult because I remember a lot. I plan to take at least 15 credits per semester because I plan to double major and plan to graduate in four years.

Part of the reason why I want to take 18 credits is because:
1.) I want to have most of my prereqs and general ed. classes done before sophomore year
2.) I plan to transfer to another university
3.) I’d rather get Calculus I and II out of the way since I already took the class and have prior knowledge.

ALSO…

If I decided to take 18 credits, would federal work study be too much?