I believe if people pay 20 different visits to the fortune teller =o you get the project plan for a proper shop for it, wish i joined the forums earlier and found out visitors count towards the 20 xD I've had her visit my town twice >.<
Yep, after the 20th fortune told the mayor needs to pop in and talk to her - she'll ask to move in and you just go start the project with Isabelle (and pay for it of course.)