You can't get an average rate with 400 flyers, that's just not enough data. You'll need a minimum of 5,000 flyers to get your average. It can vary depending on several factors. The most important is going to be where you live in the first place. Most types of businesses average around .01 to .008 percent. However, depending on where you're at, the cleaning business market is usually flooded, so you should expect somewhere between .007 and .003. You won't know what it is until you do a large enough distribution to get accurate data.
Printing can have an effect on either side. You can print simple 5,000 flyers for $30 or you can print full color glossy etc etc for $300 and up. So do you want to do more flyers with simple flyers or less flyers with more expensive flyers. Find the sweet spot.
You can also take your target market data and use census data to figure out what the best areas to flyer are. You can also map out you current clients versus the areas of distribution, and run census data on that to verify that you target data is accurate.