Work mainly depends on how much you need to study. Some can work more, some need to work less. Almost everyone I knew in school worked. Starting part-time is probably better. Maybe around 20 hrs/wk, give or take. Once you find out your studying needs, then you can alter your working hrs.
I don't know if you are going to be a CNA, but see if you can find a job that will allow you to study when thing are quiet. I always hear people recommending a CNA job, but they get worked to the bone. 12 hrs, nonstop, and you will get in trouble for studying on the job unless the floor is cool with it. They want you working, not studying. Having a little extra study time can really help.
Make sure that you make time with your fiance. School can be consuming, so you and your fiance have to make an effort. Go on dates, even quick ones. Allow your fiance to participate in your studying. Let he/she help test you, hold the flash cards, or you have your fiance be the practice dummy for your assessments. Keep it involved. Sit together when you study. Put the books down during meals and talk. I was in a relationship during school and it didn't turn out well. It's hard to have a relationship when you put school ahead of the person. Both are equally important.
I tried to work on the weekends, afternoon and evenings, and had my weekdays open for school.
Make sure you get enough sleep. If I had to work on a weekday, may schedule looked like this. School from 8-12, home for 1 hr, then to work until 11. It was a 14 hr day. Then clinicals at 6 am. Try and space it. Take naps when you can.