It often depends on the project. A 30% deposit is payed upfront and secures my availability. The rest of the project is split into two instalments. The second payment of 30% is due half-way followed by the final 40% upon completion of the project.
There are two benefits to this. Firstly, you are in control and do not pay me unless you are happy with the project and its progress. Secondly, it is often preferred by clients to have the project cost split up into individual payments.
I am flexible in on the payment terms so feel free to get in touch if you have questions about this.