You need to work the comp plan backwards. It sounds from your post that you are talking about commission only. So you need to take a decent wage for your area and make sure that can be earned in the first year. The percentage comes last, not first. Start with the wage, ex/ 75k for Philadelphia, then work backward with the expected results regarding average sale, average life of a client, length of cycle to go from prospect to client, and then client to posted payment. You'll need to "feed" sales people with a pipeline which should make up about 30% of their own prospecting efforts. You want you people closing, not cold calling. If you have a subscription based product or repeat orders, then include renewal or residual income so that the second year forward far surpass first year income. Equity stake or a performance based stock program is essential because the leaders will always be recruited by other companies. You have to make sure the performance expectations are reasonable in regards to your sales cycles and how much lead generation you expect from sales people. No matter what, a commission only opportunity must have much higher earning potential than a base + commission or the risk isn't worth it for the salesperson.
Happy to discuss if you need more info...