[It's totally my opinion from my little experience] In Canada (Or North America and Europe), a basement is available in almost every house. People generally use it as a storage area, like keeping their washing and dryer machine, all big items that are not needed and kid's toys. Because it is under the ground area of the house, there isn't enough air and light. It's like cold storage, the whole year you will feel cold in this underground space.
Now, new immigrants started buying their houses, including the old immigrant. Most of these immigrants don't have enough money and the house prices are too high to catch. So, they somehow just manage the downpayment and bought the house on a mortgage (Bank loan). Each month they must pay their monthly premium. And, that is not a small amount that anybody can manage. So, these owners don't have any option but to rent their basement.
As I told you earlier, these areas were made to make storage (I guessed), so it is not the best well-maintained area. In some old houses, there are holes, moles, cockroaches, mice, and even bed bugs in that area. A new homeowner already expended a lot of money to buy the house, and now they don't want to give more effort into its renovation. If without full renovations they can earn money by renting it, then why wouldn't they?
The immigrants who migrated from other countries, they already expended lots of money on fees and other expenses. Especially the students. they can't work full-time to earn money, so they have to survive with a limited amount of money. The only option left for them is to rent basements with some other students. Now no matter how much trouble they face, they have to adjust to it, because they can't expend more money on this, rent is really expensive in Toronto and around the Toronto area. They can't complain to their parents or guardians in their home country, because they will worry and ask them to come back. They can't complain to any authority (If there are any who can help) because they will be kicked out of that home and other homeowners will scare to let these people rent again.
Apart from this problem, there is another big issue, the reason I have started writing on this topic, which can be solved. I think it's time to think about it. Basement means it will be under the ground. Which is always a cool area. The room temperature of the main or top floor isn't the same as the basement. These three areas have three different room temperatures. The top floor is too cold in winter and too hot in summer. The main floor is in a better situation. But the basement is always cool. It's too cold in winter, in summer it is always a suitable cooler than the outside and other floors. But in a house, the heating system can't be regulated differently. So, the house owner controls the temperature according to their need. Which doesn't matches the basement environment where tenants are living.
The heating system runs with one controller, from the top or from the main floor. So, when they felt cold in winter they turned on the heating system and whenever they felt the room is warm enough they turned it off. What happens who live in the basement? They were still cold, but the landlord from the main or top floor turned off the heating system, so they had to live in cold storage. This is inhuman. People felt sick, but again, only people who are on minimum income or students live there, they can't do anything about it.
In summer the top and main floor become hot and the basement stays comfortably cool. The top floor people who have the AC/Heating system controller turned on AC. The basement doesn't need that but they had to keep their place cooler because of the top floor. Again in C30+ temperature outside, the basement people had to wear a jacket and turn the heater on to survive. This is just a big waste of energy.
A big amount of energy can be saved just by making different heating and AC controller on different floors in the house. I think Canada, it's time to make that change. It will be a better living standard in the houses and a big save of energy and money for the homeowners.