(this is all assuming that you have a lot of confidence in this sponsor as far as the sites creating sales)
I was gonna suggest that you find content for 4 free sites (all the same niche) & start there. Build all 4 using the same template - switching around the ad text & titles & banners & whatnot (and of course the content
) This method should only add an hour or so to the process. Submit one of those sites today, one in 30 days, one in 60 days, one in 90 days.
Tomorrow, pick a different niche & build 4 more. Submit the 1st one tomorrow, the 2nd one in 31 days, the 3rd in 61 days, the 4th in 91 days.
30 days from now, you won't have to build a free site for a long time
The spacing will be fine, because no submitter is going to care (assuming for some reason they did remember) that you used the same niche/template 30 days ago.