you can find someone to do a logo for really cheap. if it gets more illustrative it might cost more, depending on person.
you could pay anywhere from free to 25 bucks to 100. i woudl say between 50 and 75 is not bad. this sounds like alot, but keep in mind that basic logos from a marketing firm can be from 300 to the sky. dependin gon the business.
might be cool, but i dont think any of us need a 300 logo. steve has provided alot of good ones here. you could use one and tweak it if needed.
just make sure that whoever does it, especially if your paying 50 or more bucks, provides you with a vector based digital file. yes a photoshop file like psd, jpg, tif, eps, etc. will work, but a vector pdf, or ai, or whatever will work best for you. without getting too technical, a vector based file is scaleable to any size without losing quality. it can be printed on a golf ball, or a billboard with equal clarity. also, if it is more than one color, the designer should set up the spot colors and seperations. maybe even going so far as to designating pms colors. to keep the colors consistant for Ts and stuff. depending on how you print.
check places like http://logopond.com/
for inspiration. not much in landscape or yard care, but there are alot of VERY good logos and looking might spark a good idea.
i hope you find what your looking for.
if you need help, or find somethign and need it tweaked let me know.