Hi MuMin-san,
Here is BC's Residential Tenancy Agreement. To make short, the owner can't charge extra money by law. I'm the owner of small apt., I don't ask money at least the guest stay over 3month.
Good luck!
11. OCCUPANTS AND GUESTS
1) The landlord must not stop the tenant from having
guests under reasonable circumstances in the
rental unit.
2) The landlord must not impose restrictions on
guests and must not require or accept any extra
charge for daytime visits or overnight
accommodation of guests.
3) If the number of occupants in the rental unit is
unreasonable, the landlord may discuss the issue
with the tenant and may serve a notice to end a
tenancy. Disputes regarding the notice may be
resolved through dispute resolution under the
Residential Tenancy Act.