I might be riding a fine line with respect to the no advertising policy here -- if I've crossed a boundary please let me know, and feel free to remove this post.
Anyway, all the points made in this thread are great, especially in regards to buying quality equipment. Don't skimp, or you'll regret it. Investing in the highest quality, well researched gear you can afford will enable you to do your job faster, more reliably, with more confidence, and less downtime due to maintenance issues.
I've worked with a handful of service companies as a software developer, including landscaping and lawn maintenance companies in the past, and another point that cannot be ignored is the importance of properly managing your business information. Especially with a small operation, writing quotes, handling invoicing, following up when and where needed, and adequately tracking your customer relationships can quickly become a nightmare that chews up a lot of time that you should be spending more effectively out in the field. You also have to worry about projecting a professional image to your customers, and letting administrative items slip through the cracks is a sure way to lose their confidence.
Of course this is the kind of stuff that computers are perfect for. There are a number of systems available to help you manage your business information, and they all have strengths and weaknesses. A lot of them are marketed as either 'Field Service Management' or 'On-Site Service Management' systems if you want to do some searching around on Google for them. The features and limitations that distinguish one from the other are far too broad to get into in this post, but if anyone has questions about the technical differences and implications of specific systems, or even generally speaking, I would be happy to contribute what I know.
Anyway, as a software developer I've put a lot of time and effort into the On Site Service Management System that's linked in my signature below, and I really think it's a high quality example of what effective business information management can do for you. My partner and I are in Public Beta right now, so it's completely unlimited and free to sign-up and use, which is why I feel okay mentioning it here. The feedback that we received from our closed beta testers has been fantastic, but we're always looking for more suggestions and opinions on what we've created. You guys and girls are the experts after all!
Best of luck to all of you brave entrepreneurs! Taking the risk to run your own business is a great and respectable thing to do, and so much of our recovering economic strength relies on people like you making the sacrifices, and experiencing the thrill and uncertainty of running a small business. Bravo.