Depends on the villa, last time we went Friday to Thursday. Next month were staying
10 days Monday to Thursday, (our choice). Some management Co.s/ villas will want you to begin the day its availible usually Fri-Sat or Sun. Some are more flexable.

Have only rented once, but it's different than the typical mainland US. You have a limited supply of people coming in due to flights, not like driving in. So they typically have a 1 week minimum, starting any day that it's available, you can book an odd # if you prefer, we just did 8 nights because it fit our schedule.

FWIW - we booked early on so it was wide open. Later in the process as it fills in, I could see that they'd get a day or two here and there and would prefer not have any downtime, but not sure how they deal with that. In our case, there were 4 nights open after us, and we were told the owner was coming in to stay and do some things prior to the next rental.

I have used http://www.mclaughlinanderson.com/ several times and just love their customer service. There Villias are top notch. You can rent there Villias anytime of the week. You are just required to rent for a week.