After 100 years you (your grand children) will get a notice stating the lease is over. You would then have two options.It is a model lease template, built for Philadelphia's landlords and tenants, which is easy to understand and amend and is downloadable for free. You flat will be leasehold only as you (or other flat owners) don't own the actual land. By default (unless otherwise mentioned) it is 99 years. Yes, your lease is valid. As long as it has all the relevant terms, like the price, party names, etc. Anyone who purchases a residential or commercial property will own it only for a period of 99 years, after which the ownership is given back to the landowner. The Guide explains what you should know when applying to rent, living in a rented property, and dealing with the end of a lease. You need a Rental License to rent out a property.