Congratulations on your graduation. Now, with regards to the military and the recruiter: If you don't have it in writing, it isn't guaranteed. Have a good look at your ASVAB. (Armed Services Vocational Aptitude...). Anyway, this will let you and your recruiter know what MOS or rating you could possibly qualify. There are lots of great jobs that you can get in the military. I enlisted in the USCG on my 18th Birthday, I wanted to be in law enforcement and of course, as a under 21, that is nearly impossible. Except in the USCG where a boarding officer (E-4 and above) assigned to maritime enforcement has the same duties as a US Marshall. I didn't end up taking a Police job afterwords, but I had a great experience. I was a mechanic and got to attend some great trainings, got to see and do a lot of cool things. In a civilian world, those skills are desired and you can easily transfer them into a civilian job.
Really consider your rating and job. Each job serves in distinct duties. Personally, if I had to do it again, I would have seriously considered HVAC or Culinary, or healthcare. The Army Corps of Engineers or Navy Seabees are great options too.
"Pick your rate.... Pick your fate". True for any Armed service branch.
Don't rush into it too quick. This is your future after all.
Congratulations.
JustinG