Realtor commission on CD

I got a CD offer for $15,000 down and $700 per month on a $70,000 home. This offer was given from the realtor. She wants her full commission up front. Is this normal?

I have a problem with this because they’re taking one third of the initial down payment from the buyer and I have to wait another ~10 years to get the full money. I don’t understand why the realtor should get their full payment immediately.

What can I say to the realtor? Is it possible that they just get the percentage of the down payment based over the years that it’s paid off and I send them a payment monthly?