What's the best way to buy this house?

[Aaron Rosenberg]

Meet Husband, Wife, and Mom.  

Husband and Wife are pre-approved for $900k in loans, looking for a 2-family house.  Husband & Wife will occupy 1, Mom the other.  

To make the down payment, Mom will sell her fully-owned condo for $500k or close to it.  

I think Mom should buy the property using a 1031 exchange to avoid taxes on the sale.  Other than that, what other advice would you give this lovely couple and their dear, sweet mom?