The wait for an invitation from Spotify varies according to which country you are in, how many people are on the waiting list before you, how efficient the Spotify servers are running. It probably averages out around a week or two but can take longer.
From their website:"Spotify free is currently in an invitation-only beta, which means you need to have received an invitation token to access the service."
To join Spotify you will either need to know someone who has a spare invitation they can give to you or wait until you move up the waiting list.
If you are paying for the premium service from Spotify they give you an invitation code when you make a payment. You can pass an invitation code to your friends who can then join Spotify by entering the code into the invitation form (See links below). Although the main Spotify service is currently invitation only they have started a time limited open service.
Spotify are not currently holding a waiting list. The only way to join is by paying for a premium account or finding someone who has a spare invitation they can give to you so you can join the free service.
Working out payment arrangements with the artists/record labels.
Spotify is a legal free streaming music service which sometimes imposes an invitation system to limit the number of people joining so that the system does not grind to a halt. When there is not so much pressure on the system then an invitation is no longer required and anyone can join at any time. The invitation system operates at different times in each country as needed. It is possible to bypass the invitation system, which is unlikely to result in a legal prosecution, but you are liable to be blocked/disconnected at anytime.
Most likely until the end of the billing period during which you cancelled the service. Spotify does not issue partial month refunds.
Take away their invitation.
To use the Spotify app you need to have a Premium account with Spotify. You can then either stream music to the phone with your Internet access or synch with your computer and take your offline music if no connection is available. (See links below)
Generally, an invitation to treat is not an offer but an indication that a person is willing to negotiate. If the other party rejects the invitation then no negotiations take place.
on spotify its 7 : 16 BUT on youtube its 4 : 48