To summarize, under age 31 to hire on, must retire at 56, you'll get paid to go to the OKC ATC academy, then paid $31,700 (plus locality or COLA) at your first facility, then there are pay raises as you meet milestones toward certification.
The MOST money you will make will be at a facility in a high cost of living area PLUS the highest pay. Certainly, LA center is close to the highest paid, with an ATC-12 pay band and about 22% locality pay.
So, after 3 or 4 years, you get checked out, your pay is ATC-12, or $74,950, plus 22% locality.
Should you go to Podunk tower in No Wheres Ville, you'll get ATC-4 pay after you check out in about one year, or $37,200 plus the lowest locality pay of about 11%.