Can a landlord cancel the lease before I even get a chance to buy the business out of receivership?

A landlord generally keeps its ordinary rights under the lease and general landlord-tenant law, and those rights aren't automatically frozen just because a tenant is in financial trouble — if rent is unpaid or the lease is otherwise in default, the landlord may be able to act, including terminating the lease, before any formal insolvency step is taken. Once a receiver or trustee is actually appointed, courts will often grant a stay of proceedings preventing landlords and other creditors from taking steps like terminating the lease without leave of the court, but that protection generally only exists once the formal process has started, and only to the extent the stay covers it.

If you're interested in a struggling tenant's leased premises, timing matters: acting quickly and coordinating directly with the tenant or the incoming receiver on preserving the lease is far more effective than waiting, since a landlord's ordinary remedies remain live right up until a stay or formal proceeding is actually in place.