Hey I'm currently a first year, there's a few things that should probably be added.
1. What is each residence like? And which is the cheapest?
There is already a thread on what each res is like and it's pretty accurate.
Cost: While some of the accommodation is a lot more expensive (e.g. someone said their fortnightly rent was $500+ in the new built macquarie village, while someone in towers said theirs was around $300) your youth allowance covers you for a lot of it. I know when I first applied I accidentally added it up wrong and told them I paid less rent than what i really did, so when I updated it to the higher amount the allowance payment went up to help cover more of it. And considering you have to move to attend the course (that's if you don't live within 90mins travel time of a similar course like the one offered at UWS) then they will cover you for it, plus you get $4000 relocation grant at the start of the year then $1000 mid year from centrelink because you had to relocate to do the course.
2. Is there any accommodation that has more first years in than others?
Unfortunately not but that seriously does not matter one single bit. The selection is always mixed but you will always be with other first years. Though having second and third years around does help because they can give you all the inside knowhow. And the paramedic course is the largest cohort followed by policing students so there's a good chance you will have other first years doing the same course with you.
3. Do many people living in self catered places get meal plans?
Not sure sorry. But the food is pretty decent.
4. Is it easy/possible to get a part time job? If you are on package 1?
Getting the job is hard if you're not fast. Most people have a blast at O week (best week of your life), and forget to look for jobs, so get out there quick while you have the O week spare time and apply for the jobs the last 3rd years left behind and before all the 2nd and 3rd years come back the following week. But yeah package 1 makes it hard.
And btw the catered food isn't that bad. They're not gourmet, but they're good enough, better than hospital food.
On a final note, living on campus is a lot better than you probably think. So many people I know get campus sick (like home sick) when they have to go home for the holidays because they miss their dorm family. What some of people do is live on campus for first and second year then live off for the third once they're over it and have their solid group of friends. I have friends that went straight to off campus and regret it so much, the person above makes it sound tacky and like its a nuisance but its honestly as lively or quiet as you make it. You have a lock on your door for a reason and it makes studying easy when you need it.