"Purchase and rehabilitate an existing structure that has been completed for at least one year."
You can purchase any home you want to as long as its been completed for at least one year. There are several brand new homes that have been completed and sitting for a year waiting for someone to buy them. This is often the case when a builder does not finnish the kitchen , trim etc and they don't want to invest the money in the details. I hope this helps.
And have yet to come across a similar purchase/rehab conventional loan with 3.5% downpayment, one time closing, fixed rate, 30 years.
There are loans available for newly built/unfinished properties which require a minimum of 20% downpayment and proof of clear title.