The Vastu Shanti Puja is performed if the person faces financial crisis which is caused due to choosing the property against the Vastu parameters. And if the interior of the house is against the Vastu rules. One should perform the puja when one purchases an old house.
This puja should take place when renovation takes palce in the house or office of the person. One should also perform it if the person is returning from abroad or a trip after very long time. A person can also perform it after a long time of living in the same house.
The art of performing a Puja or a Ritual at Hindu households has always remained a matter of concern unless you have a "Family Pandit".