I think most of people in this thread really don't understand how PhD funding works. And can be really discouraging with their comments.
At the time of admission there is an offer of funding or no offer at all. Sometimes for only one year, sometimes for several years. In the case of OP, funding is guaranteed for 56 months, which is the minimal expected length to complete a PhD. The only way to lose the funding under these conditions is usually by not passing the courses, not passing the steps required for the PhD (defence proposal for instance, comps). This can happen but rarely. PhD students usually have a very good academic record. Failing the doctorate can be related to various personal factors, rarely to the academic level. If OP failed as PhD student failed then he will no longer be in the program.
Stating that funding is not guaranteed is like saying to an employee who wants to immigrate "your job is not guaranteed because you can always get fired". There is no guarantee for anyone then.
Also, there is not always a "contract" for the fellowship. By federal or provincial granting agencies yes, but universities rarely. If from the university, the funding can take different forms: grant, research contract, teaching contract etc. This is arranged when the academic year starts. A PhD student can decide to not TA for a semester and hence get less funds.
Finally, 25000$/ yr might not be enough for some of you. If you deduct the tuition fees, the amount is in line with the immigration requirements. Therefore, there is no reason to reject the app based on a lack of funds. Whether some people here find it insufficient is another debate. But this is not going to help OP's case by pointing to a false problem.