It depends on your specific need - some parking spaces are easier to find than others. So to make the most of the site we recommend that you send 8-10 messages and allow a 7 day turnaround, although it is likely you will gain a good number of replies within days. Many listings also contain mobile phone numbers which will allow for immediate contact. If your first round of emails don't introduce you to the right person, simply send out a second round the following week - there will be more people to choose from and you are likely to succeed within that week. You may also need to consider varying your expectations (perhaps offering an increased rental amount or longer rental terms if the parking space is in a high demand area).