Millennials are moving out of their parents’ basements and into their own homes. The average age of a first-time home buyer is 34, according to online listing service Zillow. This new generation of buyers enters the real estate market with high expectations, but soon collides with reality, often in the form of their HVAC systems.

Zillow partnered with home management platform Thumbtack to survey 1,000 millennials about their expectations for work done to a new home and compared that with the sites’ own real-life data. The survey found that the average millennial expects to pay between $10,000 and $15,000 to make a home move-in ready. However, the data shows new homeowners should actually expect to spend about $26,900 on these projects. Evaluating, repairing, or replacing HVAC systems is the most expensive move-in project, costing $3,615 on average nationwide, according to Zillow.