You can query the Invoice table to get this information:
http://help.infusionsoft.com/developers/tables/invoice
Use this method to make the query:
http://help.infusionsoft.com/api-docs/dataservice#query
Example:
$returnFields = array('Id','FirstName', 'PayStatus');
$query = array('ContactId' => '5');
$contacts = $app->dsQuery("Invoice",10,0,$query,$returnFields);