Hypothetical Financing Scenario

[Joe Doman]

Hello all, I wanted to check in with the community to see if the following scenario is even possible:

If a seller is willing to carry back a portion of the purchase price but wants a substantial down payment, can I go to a bank to get financing for the down payment? 

Say the purchase price is 150K, seller wants a 100K up front and the remaining 50K will be paid off in monthly principal payments. Can I go to a bank and say the purchase price is 100K and leave out the 50K seller financing piece. Is this legal? Ethical? -Would like to hear your thoughts. Thanks!