A friend of mine sent me this link earlier;
www.reddit.com/r/IAmA/comments/quh9y/iama_selfpublished_author_who_quit_his_day_job_ama/
Its quite a long read unless you skip to the questions which interest you, but he is very thorough and may give you some useful insights into self-publishing, agents & royalties. I also think he comes across as a genuinely nice guy too.