I would expect that the landlord would not want to rent out a 2 bed apartment to only 1 person on the lease (regardless of how the rent payment was split between the tenants). If they looked into Chantal's income stream enough to say "uhhhh no, youtube is not enough to pass our credit check to lease you this apartment" then they would look at Peetz' call center job and say "uhhhh no, you cannot support a 2 bedroom, split level apartment on this income". Plus also landlords need to know who they have living in their units even if a specific person, such as a child, is not paying towards the rent due (OK, I don't have experience of Canada, but it's a pretty common requirement to know how many people, and who they are, that live in your units even if you don't about how they choose to split the rent between themselves).
If there were any issues with the credit check regarding Chantal's YT income, I think she would just lean on Mama Sarault to act as a guarantor. Pretty sad to do so in your mid-to-late 30s, as that's more the kind of thing that students and those fresh out of college have to do, but she could easily convince Mama that the big nasty landlord wouldn't accept youtube-bucks but Mama is totally proud of her and recognizes she is a successful content creator and so will sign on the dotted line.
Even if it really was just in Peetz' name and she does a runner, they are now on a rolling lease and so he just needs to give 1 month's notice. I would expect his mother would help out on the final month, if they were financially able to do so. But if he got out during that month then yeah he may get sued in small claims for the missing amount but in the grand scheme of things it wouldn't be too onerous on his finances if he was able to negotiate a payment plan in the event he couldn't pay the full amount at once. The main thing is that he isn't be solely tied in to a year's lease just in his name that he has to abandon early.
