+1 on what prof said...
You can find a decent used moped on Kijiji
for less than a 1000 most days. Tomos mopeds are well supported in Canada too.
Your looking at a 1000 to do a decent DIY electric power setup and 1500-2000 for a factory built with reasonable power and range. I've been down that road some and talked to a few E power guys who went the cheap cheap route, they bought and built twice which of course is no fun.
Food for thought...If you want to be 100% legal a DIY E bike in Ontario isn't what your after either, a DIY E bike is close but still not 100% legit. In most parts of Canada if what you want to ride is powered by anything other than muscles it has to have the federal government's stamp of approval on it to be 100% legit.