I've done interprovincial moves several times, and also moved from Ottawa to Toronto. This was as a single person. I also have married friends who have done the same.
One person needs to gets a great job first. A job that person is really, really excited about. Do everything you can to find a job that will pay relocation costs. It won't cover everything, but it makes a difference. You can also deduct some expenses on your income tax. Make sure you optimize this, so that if there is a maximum on the job relocation costs, you are able to deduct remaining expenses where you can on your tax.
Make sure you research living costs really carefully, including utilities, property taxes, and income tax. Hydro may be a big deal in Ontario.
Find a place to live before you move. Most relocation policies cover a trip or two to find a place to live. My late mother's advice: find a place you really, really like, even if it takes some time. In Toronto, that includes finding a place near (or an easy commute to) things you really, really like to do.
Seriously think about renting. For a long time. Maybe forever. I have wasted many thousands by buying several places in a row, and then moving on within a few years. Only one appreciated to my benefit.
Don't underestimate the time or cost of commuting. Try the commute at the times you'll be travelling.
Most provinces require a safety check of your car(s) before licensing. Ontario has strong emissions standards. If your vehicle(s) are old, a lot a repairs may be needed or it may not be possible to get the car registered. When I moved to Alberta it costs $3000 to get the various dings repaired so I could register my older Neon.
Weirdly, take it with a grain of salt what locals tell you. (For example, I was told it would be easy to find a place to rent with a dog when I was moving to rural Alberta. Not so. Rural people think dogs belong outdoors. City people think dogs belong indoors, in all the rooms in their house.)
But have fun!