When you buy a property off-plan it means you are buying a property before the developer has finished building it. Sometimes you’ll buy it before the developer has even started construction. You’ll usually pay a small reservation fee, but you’ll also have some say over the design and fitting out of the property. It’s worth bearing in mind that the offer period on mortgages for new builds are only valid for a set time. You’ll need to ensure that your property will be finished within the offer period or risk losing the mortgage offer.