Or we need to play and if we land on that particular street then we'll get it free?
Like you said, you play, land on the artist you owned a house before, and you get the card for free. If you had 5 cards from this artist, you will get up to 5 cards for free. The 6th you have to pay. The game is unrelated to shares and true fans which will be implemented later.
But speaking of shares and houses? what will happen to those if I'm not playing? Well, sorry to ask that again. I'm really can't help to wait for the fully upgraded JPA version.