Looking to start plumbing business

Hello all. I am new to this site but I am very impressed with the amount of knowledgable contractors and the great information shared by all. I am a plumber by trade, for about 5 years now. I am getting ready to take my master's test and I am very serious about starting my own business. I would love any advice from plumbing business owners, or anyone who has started their own business for that matter. I currently work for a major mechanical contractor but i am wanting to start a residential business. I have a brother in-law who is an accountant so I have that aspect covered but I have many questions about things such as getting started and drumming up new business, etc. for anyone willing to lend an experienced ear. Thank you in advance for any advice and I will continue to read all your great posts.