I work in a Sixth Form. If he is Year 12 as long as he is on time, attending lessons, engaged in classes and not skipping the careers/tutor time/PHSCE stuff he is doing OK.
Check his lesson attendance. Check his reports. If you are constantly getting absence notices from school/college (check your spam in case automated messages are falling into there) or he is always late - he needs to improve. If his school reports are in in the "not good enough" area - he needs to improve.
If all these are on track then he is OK. He is getting by on his brains. He maybe able to fit the homework/coursework in during frees/study periods. This is OK.
But Y12 is often a transition into how to work independantly. The motivation to crack on and put some effort in often does come when he has a goal.
Has he had Y12 exams yet - maybe the results of those will prod him into working a bit harder?
And maybe you do need to sit down with him and chat through post-18 options. Look at your school website - is there a SIxth Form newsletter/bulletin? Ask him to, by the end of half-term or after his Y12 exams, have 3 unis he wants to visit and you will help him arrange them. He is not commiting to going to those - but it will give him an idea of what is on offer. And if not, what is he doing - degree apprenticeships? Ask if he needs to see the careers advisor (there should be one at school/attached to school). If he refuses, then ask him to arrange to meet with his tutor or head of year to get some guidance.
Give him a deadline to work to and some ideas of targets.
Money/job - let him run out. Don't lend him any but offer jobs as a way of earnign (or he can come an weed my front drive if he likes...I'll pay him a tenner). Come Y13 he maybe better focussing on school work that part-time jobs anyway - so as long as he is building some experience I wouldn't fret too much about this.