Nothing builds confidence like successfully doing something. I started small and worked up to larger jobs. One thing I would advise is NOT mislead your clients into thinking you can tackle anything. Some things must be overcome which take time, ie building a work force complete with equipment, trucks, a management system etc. You cannot do a job with a labor figure of $150,000 with two men and no office help and do it on schedule, bid other jobs and handle service work. If you bite off more than you can chew it will come back to bite you in lost customers and people who will think you're incompetent.
Don't be afraid to say "I can't tackle a job this big at the moment". You will always have to tell people NO from time to time or you will have a black eye! It is not a weakness to say no. It is a weakness to say nothing when you should say no.
One bad experience with a customer and you've likely lost him for ever...
