When I retired I started my own business. This coming spring it will be 8 years working at it. Paid for my initial investment in the first year. I make good money and still cover my overhead costs. I owe no one except my wife. She's my bookkeeper. I hate that stuff. All of my business comes to me by word of mouth and/or by referrals. I do not advertise. I keep it small and don't allow it to get big. Big jobs bring their own problems so I choose those carefully. Customers will be your most difficult aspect to deal with, followed closely by their spyders. Learn when to refuse a job you shouldn't get into and DON'T do it. Your client will be your first clue when to refuse a job. There's a boatload of excellent advice preceding mine so pay close attention to it and good luck. Stay happy with what you choose to do. OOP's, something I forgot to tell you. Do not borrow any money to get your business going. Do it all on your own dollar.
One of the most important (among many) of the issues brought up by 2dogs is dealing of the hunger of developing your business is in dealing with Customers, carefully resist the problem customer even more than the issue presented by the item to be worked on. I have literally thrown unreasonable potential customers out.