There's not enough information to answer the question.
How much do the items you're expecting them to sell cost?
What is the length of your sales cycle? What would you consider to be a reasonable sales volume over the course of a week / month / year?
How much effort do you anticipate the sales people will have to put in to close the sale?
Will you be providing the sales people with leads, or do you expect them to get out there and pound the pavement on their own to identify and cultivate their own leads, or a mix of both?
Will you set non-negotiable price and terms of the sale that your sales people just have to deal with, or will you allow them the flexibility to negotiate terms with their customers in order to close the sale? Or will you treat them as independent dealers or resellers who have the ability to totally set their own prices and terms?
Real estate agents will kill for a commission one third to one half of what you're talking about, but because the homes and commercial buildings they sell cost so much, even a small percentage on a single sale works out to a large check.
On the other hand, if somebody's selling relatively inexpensive stuff, they're going to have to sell a ton
of the stuff to make a living. That's a volume business -- they're not going to be willing (or able) to spend tons of time on each sale.
But unless they can move truly massive quantities of product very easily, their commission percentage will probably need to be higher on a per-item basis in order to make it possible for them to make a living at any reasonable sales volume level.
IMO, you need to do a bit of homework to find out what salespeople in similar businesses to yours typically make in your area. Figure what you think is a reasonable sales volume. Compare the amount of legwork and "selling" that your people will have to do compared with others in similar businesses.
The answer that's right for you and your business will, I feel fairly certain, start to become more clear. At the very least, you'll have some evidence and justification for whatever decision you make.