I don't do yellow page advertising anymore. You'll do much better with direct mail. Our best form of advertising comes from a self-styled piece we distribute. We have pulled together other trades and allowed them to buy 1/4 page ads for only $40. We're not in the advertising business. We make our money plumbing. The idea with the book is that it has numerous trades (sheetrock, electrician, hvac, etc).
If you go with newspaper advertising, you get one shot at a phone call. If you go with yellow page advertising, they have pages of competition to call. If you go with your self-styled book of trades, homeowners tend to keep those booklets in a drawer (just in case). It generates lots of calls and it is CHEAP. We distribute door-to-door and we distribute to every real estate office in town.
The other tradesmen will also automatically refer their customers to you. It works great. Best money-maker advertisement I've ever done.
How much will you make? Your plumbing calls will range from $250+ on about every call. You'll have some cheapie (toilet unclogs) and you'll have some more high-dollar stuff. But you'll average $250/call easily.