Stepping out your back door to roll putts whenever you want changes your entire routine, and getting the sub-base and drainage right means it actually rolls true year-round. An install usually takes a few days once the crew breaks ground, but scheduling it during the dry off-season is where you save real money because landscaping contractors are hunting for work and pricing gets flexible.
A typical US project runs about $2500, but that price swings based on your yard's slope and how much old sod they have to haul away. Get at least three quotes from local turf installers so you can spot the outliers and negotiate on labor before you hand over any deposits.
Remember that the 18-month intro window is a strict deadline rather than free money, and any leftover balance when it ends will trigger high interest charges on what you still owe.