You do not need to be home for cleanings. In fact, the most important thing we recommend is making sure there is a reliable way for your Homekeeper to get into your home. We generally recommend a garage code or a lockbox, because it is more secure than leaving a key under the mat (although you can do that too).
Here is a lockbox that some of our clients have used: http://www.amazon.com/Master-Lock-5400D-Set-Your-Own-Combination/dp/B0002YP1VC/
TIDY strongly recommends NOT giving keys to Homekeepers. The safest thing to do is retain control of the access to your home.