If you are going to be a legal resident of Manitoba, you might very well qualify for the same public health insurance that is available to all Manitoba residents. You should contact the province of Manitoba to find out. There are some exceptions, but if you are coming to Manitoba to work it seems that you might qualify.

There would be a three month waiting period, so you should certainly have full coverage for three months. Keep in mind that the public health insurance in Manitoba may not cover everything. You may need to get insurance for things like drugs, dental, eye care (for example - I don't live there so I don't know what gets covered). So you may wish to maintain supplemental coverage for your entire visit as well, or be prepared to pay out of pocket.

If you are coming to work, your employer might offer supplemental health insurance as an employment benefit, so you should check that out too.