The usual default rule is that a purchaser is bound to honor a lease on the same terms as the previous owner, and that purchase agreements are subject to existing valid leases.
However, the Ontario Residential Tenancies Act, 2006 (S.o. 2006, chapter 17) section 49 (2) says:
If a landlord who is an owner as defined in clause (a) or (b) of the definition of “owner” in subsection 1 (1) of the Condominium Act, 1998 owns a unit, as defined in subsection 1 (1) of that Act, that is a rental unit and has entered into an agreement of purchase and sale of the unit, the landlord may, on behalf of the purchaser, give the tenant of the unit a notice terminating the tenancy, if the purchaser in good faith requires possession of the unit for the purpose of residential occupation by,
(a) the purchaser;
(b) the purchaser’s spouse;
(c) a child or parent of the purchaser or the purchaser’s spouse; or
(d) a person who provides or will provide care services to the purchaser, the purchaser’s spouse, or a child or parent of the purchaser or the purchaser’s spouse, if the person receiving the care services resides or will reside in the building, related group of buildings, mobile home park or land lease community in which the rental unit is located. 2006, c. 17, s. 49 (2).
I take that to mean that IF the purchaser intends to reside in the unit (or have one of the people in (2)(a)-(d) reside there), then and only then, you can be given notice to leave. Acceding to par (3) of the same section the notice must be at least 60 days, and must be to the end of a rental period (probably a month), and that 60 days may not start until after the landlord has actually signed a sales agreement for the unit. And the landlord can only do this if the new owner has specifically indicated a requirement for possession of the unit as a residence, not to rent to someone else.
You may want to seek out a tenants assistance organization, or possibly a lawyer, since it sounds as if the landlord is going beyond what the law permits.
EDIT:
As to showing the unit, section 26(3) of the same act provides that:
Entry to show rental unit to prospective tenants
(3) A landlord may enter the rental unit without written notice to show the unit to prospective tenants if,
(a) the landlord and tenant have agreed that the tenancy will be terminated or one of them has given notice of termination to the other;
(b) the landlord enters the unit between the hours of 8 a.m. and 8 p.m.; and
(c) before entering, the landlord informs or makes a reasonable effort to inform the tenant of the intention to do so. 2006, c. 17, s. 26 (3).
and section 27 (2) and 27 (3) further provide that:
(2) A landlord or, with the written authorization of a landlord, a broker or salesperson registered under the Real Estate and Business Brokers Act, 2002, may enter a rental unit in accordance with written notice given to the tenant at least 24 hours before the time of entry to allow a potential purchaser to view the rental unit. 2006, c. 17, s. 27 (2).
(3) The written notice under subsection (1) or (2) shall specify the reason for entry, the day of entry and a time of entry between the hours of 8 a.m. and 8 p.m. 2006, c. 17, s. 27 (3).
So it seems that the landlord may show the unit to prospective purchasers during reasonable hours. However another provision says that the landlord may not interfere with your "quiet enjoyment" of the premises, so the frequency of showing probably must be reasonable.
