An applicant will be found to be medically inadmissible if their condition will cost more per year to treat than a certain threshold number. I believe it is around CAD$6700-something.
However, before you are rejected, you will receive a "fairness letter" notifying you of the situation and you will be given time to respond. Fairness letter responses typically focus on rebutting the conclusion that the cost of treating the condition will exceed the limit. Even in the case of rejection, appeal is possible and appeals have a decent chance of success.
Demonstrating the ability to pay for the treatments yourself will not help. In Canada, if the health system covers treatment for your condition (and it covers just about everything), then you as a PR would have a right to the treatment at no cost to you, and the government has no ability to enforce a promise to pay or to force a co-payment from people who can afford to pay.
I suggest you prepare now to gather the documentation you will need in case you receive a fairness letter. You should also consult with an attorney, preferably one with experience in medical inadmissibility, to discuss your chances and your options.
Good luck.
