Rowth of sub prime lending; Is this a viable business model for lenders?

As my research topic is; Growth of sub prime lending. Is this a viable business model for lenders? (in the view of the current credit crises)

Please the focus should be on topic literature in which we are going to look in; not the background of the topic.

2ndly; our main focus would be on mortgage loans as for as other sub prime lending e.g; Auto loan or credit card loan etc&

3rdly; the most important thing; in Introduction we must say; what are we looking at and why? And what would be the research question or questions.

4thly; please provide maximum relevant references and use only Harvard referencing style.

Finally; this chapter is very important to me as its acceptance will allow me to go ahead. Further; if this chapter is accepted by my tutor, I would more then happy to order full dissertation from your company.
Thanks