If you want the house empty first
In Pennsylvania, you can sell with the tenant still living there, so you may not need to give notice at all. If you want the house empty first, the usual notice under Section 501 of Pennsylvania's Landlord and Tenant Act is 10 days for unpaid rent and 15 or 30 days when a lease ends, depending on how long the lease is.
Check the current lease and notices before making a move-out plan. Read the Pennsylvania Landlord and Tenant Act, Section 501 (official text).

