How to convince a sales rep to take a commission job?

This will be brutal but you asked.

I know sales reps have concerns about working on commission i thinks it’s worth the risk but maybe i am being biased.

You are engaging in one of the most common new entrepreneur misconceptions. Virtually every new entrepreneur reasons as you do.

No, it's not worth the risk to anyone except you.

How can i get this sales rep to take the job, part time?

You simply can't. You are projecting an unknown in the future. You believe that his selling your product is a sure thing. In reality you don't know this, and neither does he, so he wants to be covered in case your projections are not correct.

If he's any good at all as a salesman, then he can do better than no draw and no salary.

Look at it (as you really must) from his point of view. You can't "even" afford to pay him a draw. From his perspective, you are a dreamer with no money and just an idea.

Your best bet - sorry again - is one of the following:

Find a young, enthusiastic sales protege who will work on your terms, who genuinely values the opportunity.

Or do the sales yourself.

You need money to make money, particularly when you require the services of other professionals who are proven in their areas of endeavor.

If you don't have any sales history, you are guessing. No one believes your guesses. Consider using an independent sales rep, or group, to get started. These organizations are more inclined to consider your offer because they have other similar lines of products and services.

If the commisson is your only cost of sales personel, then you shouldn't be too picky about recommednations and experience of potential candidate. Only thing you are intrested in is whether they can make a sale or not. Give chance to anyone who is willing to prove himself. If you present this job as a challenge and opportunity, I'm sure you will eventualy find some candidates. With this approach you can ofcourse expect more young people than old, given the fact that risk aversion increases with age.

Only thing you should be careful about is, that your salesmen don't damage reputation of your product and company, when trying all sorts of selling tehniques.

P.S. I don't know what your costs structure is, but if signing 8 clients is fairly easy, then you should reconsider whether 25% is appropriate commission rate. That's why doing sales by yourself at least on start, is not a bad idea; if you don't know what actual market response will be, it may be very likely that you are giving away either too much or too little.