Some sites will let you preview and look for sitters without registering, so you can see the options. However, if you want to get the contact information, you need to be a member. Subscriptions may be paid for on a monthly or yearly basis. The best sites will give you a free trial period, perhaps for a week, so you can try it out first. If you like it, you often have to pay an initial registration fee, in addition to the subscription costs.