I certainly recommend the resources Michelle has referred you to. Her web site is the single best resource I know for starting a collection agency.
Since you have 4 years experience, you should already know the basics about the job and the laws. Now you need to learn about business, running one, marketing, bookkeeping etc. I would start by reading books and magazines about starting your own business, including – “Starting a Collection Agency, how to make money collecting money” since that would be very specific to what you are doing. Also, network with other collectors, join groups and associations, attend seminars and webinars as well as industry trade events to learn all you can. Write a business plan, marketing plan and credit policy for your agency or use the examples found in my book, if that helps.
When I wrote my first edition of Starting a Collection Agency, how to make money collecting money in 2002. I wrote this book because I was getting so many emails, letters and phone calls from people asking me how I had started my own collection agency. This book is now in its third edition and continues to be my bestselling book. During the years as I have worked in this industry, I have received thousands of letters and emails from people with questions about starting their own agencies, which may not have been covered in that book. This compilation is to help you get your questions answered, understand the FDCPA and learn how to effectively market your collection agency in order to gain more clients and grow your agency.