Consideration should be given to the part of the country in which your business operates.
If you're thinking about paying as a percentage (which should motivate the right person) it would also depend on what that percentage means in dollars on their first several paychecks. However, I would also discuss the positions broad responsibilities (including sales and profits) - prior to hire!
For a new guy/gal to share in a percentage of a mature company's sales, the applicant would have to be really sharp! Have you considered paying an hourly wage, combined with a bonus program targeted at achieving certain sales or profit goals? It could protect you from making a hiring mistake, but also reward good performance.
Other factors to consider would be how much responsibility and autonomy will s/he have to make decisions. Do you expect him/her to be on call for flood work or after hours jobs or is this a straight 8 to 4 five days a week routine?
Are you looking for a college age guy/gal (working their way thru school) or are you looking for more of a career position with experience? Our hiring experience is that if your starting pay is too much less than what the applicant has made at previous jobs, s/he won't stay with you very long.
We pay everyone an hourly wage. We pay a sales bonus at the end of every month. This past year, our lead cleaner earned around $50k and her year end profit bonus will be calculated once the annual financial report is completed (perhaps another $2500 or $3000).