What is the difference between buying with vacant possession and buying subject to an existing tenancy?

Buying with vacant possession means the seller is contractually obligated to deliver the property empty of tenants at closing, which, where a tenant is currently in place, requires the seller to properly end the tenancy beforehand through the correct process under the Residential Tenancies Act, 2006 rather than simply asking the tenant to leave. This path can involve real timing risk, since ending a tenancy properly takes time and the tenant may dispute the process.

Buying subject to an existing tenancy means the opposite: the buyer knowingly takes over as landlord to the tenant and lease already in place, with no expectation of vacant possession at closing, and continues the tenancy exactly as it stood before the sale. These two paths carry very different risk profiles, timelines, and paperwork, and confusing one for the other, or leaving the Agreement of Purchase and Sale ambiguous about which applies, is a common source of dispute. Make sure your agreement states clearly which path your specific purchase is following, and have your lawyer confirm the wording actually achieves that.