An individual yoga class (practice) takes about 60 minutes. The class starts with the student telling the teacher how he/she feels or discuss something related to the previous class. Then there is a guided practice. The class ends with the discussion of what happened during that practice. Before the end (or in the next 24 hours if the class is via Skype) the teacher gives the student a sheet of paper with the practice of that day.
The first class may take longer, depending on how you decide to do it. This is, before you start working there are some questions your teacher probably wants to ask you. This is information about your health that will complete what you have already said in your "Registration Form" and it will help orientating your practices.
If these questions are asked at the beginning of your first class, it will last longer than 60 minutes - probably around 90 minutes. You will only be charged for 60 minutes.
You can decide to answer these questions at another moment (always before your first appointment).
If your class is about theory, the duration and prices will vary. For example if you take a two hour class, it will be cheaper than two 60 minutes classes. The price will also depend on how many people will be attending the class (more people will be cheaper per person than individually).
For classes via Skype, you can pay via Paypal, before or after the class. The copy of your practice will be sent to you after the payment is completed.
If your class is in person, you can pay at the end with cash or a credit card. You can also pay via Paypal. In this case, the copy of your practice will be sent to you after the payment is completed.