I'm right down the street here in Scottsdale and used to live in McCormick Ranch.
Is there a reason you are looking for a non-agency mortgage? We handle leaseholds on a case by case basis as long as the lease is longer than the mortgage term (assuming you are otherwise qualified). In other words, if you choose a 30 year fixed loan, the lease must be in effect for at least 31 years from the date of loan funding.
I can offer that on standard conventional loans, was there another reason you didn't want an agency product?
Feel free to call me at 480-368-7715 to discuss in further detail.