To rent cars from most car rental agencies in Winnipeg you need
major credit card, hold a valid drivers licence (the names must match),
and be over 21 years old. Some agencies allow you to "cash qualify"
but the paperwork is extensive and is not viable for out of town visitors
(check when you make your reservation). TIP: If the person who's name is on the
credit card is not the driver, then add the real driver as a second driver
(there may be a small charge for that).
There are plenty of rental agencies in the downtown area, at the airport arrivals level, and around town.
Many agencies have "weekend specials" but reserve a few days before long weekends.
TIP: If you are getting a 4-cylinder subcompact, it will drive much better with a standard - not automatic - transmission (if you're used to that).
Better Business Bureau tips.
Find Local Car Rental Offices.