I am conducting a detail study on the advantage and disadvantages of university students using student loans. Please tell me the backgrounds/objectives of student loans? Such as since when student loans become commonly used? What was the purpose of student loans? (Preferably based in the UK)

Is student loan really a convenient choice for university students?
What kind of research should I use? What area should I focus on my research?
Why do companies provide student loans to students who do not have an income?
What are the percentages of students repaying their loan?
What will my focus questions be?
Are there any concepts or theories I can apply on my study?
What kind of research philosophies and approaches can I use?
What kind of limitations will I be facing when I conduct my research?
Please provide some empirical studies or literature reviews.
Please provide as much resources as possible (e.g. web sites) for me to research on my study.