patgirls, I've been looking for precisely that myself for several months. I had tried QuickBooks when I was using a PC, but became too frustrated with its complexity. I needed to find something, though for my son's small contract business and the longer I waited the more work I would face back tracking and trying to catch up. Bottom line: I got QuickBooks for Mac and found a local accountant to help me get setup and understand a few accounting concepts. It's cost me $129 for the program and the accountant charges $150/ hour. I've met with her once so far for one hour and was very pleased with how much I've been able to learn and do. It seemed to me that most of the confusion with QB is the initial setup if you're not familiar with accounting principles(which I'm not), but once you're setup the daily input is really very simple and the benefit is having all the report functions, etc. There's got to be something to the fact that most accountants use QB.
There are other accounting apps out there, but they're not cheap (you can download trial apps to see if they do what you want). I, like you wanted the ability to write up an estimate or bid for a customer. Then if I got we got the job I could easily turn the estimate into an invoice. QB has this functionality, the other one I tried didn't.
The other option I thought about was creating my own app in FileMaker Pro, which I've used before to design a form to track info on a job I worked. I decided against that because I just didn't have enough time. I hope this helps you, if you're still looking for an answer.