From what I can figure out the more advertising you do the money money you make. It can be summed up that easily. That's partially why I'm looking at franchising because I need a better deal on the advertising in order to compete.
Google Adwords is a good, relatively-cheap way to get your name out there and their FREE LOCAL BUSINESS LISTING is invaluable. Ditto w/ Yahoo.
If I was going to give you any advise I would say focus on the advertising and the work will come. Even if you can only dedicate $500 / month to it, do it and do it well.
As you get older the biggest single cost will be health insurance.
If you have no business experience, I would very strongly suggest you begin taking business courses at the local community college. Failure to keep current on paperwork, and tax issues torpedoes more businesses than anything else. I matters not how good a plumber you are. The world is full of good plumbers. Without business savvy you are destined to fail. It is entirely possible to gross well over a million a year and still loose money.