Yes, I will take a deposit. But my deposits are non-refundable and I put that in writing. Make the deposit enough to cover your troubles if the buy fails to come through, but not enough to break the customer. Say I have a $2500 machine that a guy needs 2-3 weeks to pay/pick up. 10% down, not refundable, pick up on xx date with full balance due. Clear cut and to the exact point. If buyer defaults on xxx date, I give them a 5 day grace period. If not settled by then, deposit is lost, and said machine goes back up for sale.

If a customer is asking for terms, but does not want to agree to those terms, then it is not a customer you want to deal with anyway. Move on to the next buyer.