As more universities in Canada prepare to offer classes online for the fall semester, landlords across the country may find themselves without tenants come September.

Landlords renting out apartments or houses in "student towns" such as St. Catharines, London and Kingston are particularly vulnerable to the consequences of universities choosing to cancel in-person classes — and many Canadians have questions.

What the hell is going to happen to rental markets like St Catherines if the local universities start doing virtual schooling in Fall 2020?

— mortgagejake (@mortgagejake) May 19, 2020

Queen's University in Kingston, for example, has roughly 25,000 students, representing about 20 per cent of the Ontario city's total population.

Assuming that almost all Queen's students come from outside of Kingston (which they do) and that students don't plan to live in the city should the university conduct classes online, that's about one in five landlords that won't have any tenants come September.

Of course, some Queen's students stay in university accomodation, so the numbers may not be as drastic as that — but it still paints a harrowing picture of what could happen to the rental landscape in university towns if students don't return in the fall.

Queen's University hasn't made any formal announcements about its fall semester just yet, but other Ontario universities such as Carleton and Ottawa are already giving students the option to take classes online in September.

2/3 Almost all courses have a distance-learning option. Public health guidelines will determine whether we will offer in-person courses come the fall. If we're given the green light to in-person courses, students will still be given the option to continue with online learning.

— uOttawa (@uOttawa) May 12, 2020

Together, Carleton and Ottawa boast a student population of about 72,000 — a significant chunk of whom likely rent apartments or housing while pursuing their studies.

If those students choose not to return, thousands of Ottawa landlords could be left with empty rentals in September.

"It definitely would impact us because the students are our backbone. Students rentals is great cash flow, high income because you're renting per room and putting them all in one lease," Sorin Vaduva, an Ottawa realtor and investor, told CTV News.

In fact, some Ontario landlords are already looking at making alternate arrangements, should universities choose to offer online courses.

Already looking at converting one of my student rentals into a duplex if this happens. But my bet is school starts in September or these universities may go bankrupt.

— Jared Gardner (@Jared_Gardner) May 19, 2020

And the phenomenon isn't limited to Ontario; Victoria, B.C. has a large student community, with the University of Victoria (UVic) accounting for most of that population, at 21,800 students.

The university announced on May 11 that it would move most of its classes online for the fall semester, offering some in-person instruction where "health and safety permits."

UVic will offer programming mostly online for the fall term. While complying with health and safety requirements, a gradual return to campus for employees and a resumption of research activities is also planned.

Read the update from President Cassels.https://t.co/2bKRiwghKs

— UniversityOfVictoria (@uvic) May 11, 2020

Some students could opt to return to British Columbia's capital city even if their studies are online, of course, but over 3,000 students at UVic are international, representing about 14 per cent of the student population.

And with restrictions on air travel still in place and no financial support from the Canadian government, it seems unlikely that many international students will choose to stay in Canada come September.

Perhaps most alarmingly of all, a staggering 30 per cent of Canadian students say that they're considering opting out of university altogether this fall.

There's still a chance that many Canadian universities will conduct at least some in-person classes in the fall, but landlords may find it difficult to find students to fill their rentals — and student towns may look emptier than usual this September.