I got a landscape design done for my home from a landscaper. Is it ok to take this plan to other landscapers to see what comparable prices would get me for the same job?
It's better if you get a couple other landscapers to come up with their own design. Then, you can pick the one you like best. It's probably also a good idea not to reveal that you are talking with other designers. Cost is not everything. It's the design and how well you can work with the designer that are most important.
If budget does not allow for the design to be completed all at once, explain that you want a design that can be done in stages as budget allows. Who knows, you may want to DIY some of it.
It is not only unethical what the person wants to do but plenty people do it I'm sure. A good landscaper is worth his weight in gold..as long as he works well with his client and achieves the look they "think" they want. It is good to have a professional's opinion on this board. Most designers won't leave the design with the clients, that is considered their property until they are hired and paid for the job, right?
twelvepole's message points out a lot of good suggestions. Let each contractor start from scratch, with you telling them what you want or expect, and then let them come up with some suggestions or a design. Sit down and compose in writing what you want, what design, what plants, what materials you want used,etc. so you don't forget anything when you are meeting with the landscaping designer or landscaper.