You can start flying now. A young man I'm helping started flying starting his senior year in college. Eighteen months later he's got his 4.0 4 yr degree and will be taking his CFI in a couple of weeks. You can move quicker if you start flying while you're still in college. Make it your job, hobby, and girlfriend, and the effort all of that requires, and you can do college AND start cranking on your flight training. I started my PPL in May after my freshman year and by the following October had my Comm/Inst/MEL/CFI as well as being a full time college student. I'm not a good student or that motivated but I in eighteen months I knocked out 255 hrs and a year of college credits. On that timeline you'd be pursuing your first CFI job in September 2027.