Once they are here, you can impose some taxes, and if they threaten to leave, so what?  See the letter from "justlife" above, and my additions.  You can withhold medical coverage, limit the ability to work, audit when home values vastly exceed what their reported income covers, shut various tax shelters, and shut the immigrant investor scams.  Deportation in some cases.  Snitch lines with rewards. Note that while this would indeed hit wealthy foreign newcomers the hardest, it would also imply cracking down on the classic "All-Canadian" dodges: (1) paying the kids for being cute; (2) paying the spouse for non-existent work; (3) reporting personal items as business expenses; (4) related party scams - sell at a "loss" to my Uncle Fred.  Enforce tax laws on everyone - don't target any one group, but don't avoid either!
It would also help to raise the GST, getting some of their spending into the tax base with little ability to evade - match that with an increased low-end credit.