My terms and rules:

I will not begin work on the commission until it is marked as payed.
No NSFW work
No political/religious sensitive topics.
No images that may offense or potentially offense a third party.
Nothing too nasty, bloody, violent or gory

Not sure about how the Artists&Clients website works? Don't worry, let me explain:

For each commission job there are 4 phases:
new→ approved → paid → completed

The procedure to get the commission from an artist is following:
The client open a commission slot then contact the artist about the desired commission. This will open a new job marked as new.
After reaching into a agreement the artist edit the commission to the agreed rate then mark the commission job as approved.
The client then make the payment at the agreed rate which will be temporary held by the website. After the payment, the job will be marked as paid.
The artist then submit few sketches for review (if necessary). Then submit the final artwork. In most of cases, the artworks will come watermarked.
Once the client feel that the the final artwork is good to take, they mark the job as completed. This will remove the watermarks from previously watermarked arts and the payment will be released to the artist. This completes one commission cycle.

Note: During the entire Commission process, both the client and the artist can send messages and files to each other anytime as will.

Also the commission job can be cancelled anytime by the client during the new and the approved phases. It can also be cancelled by the artist during the paid phase. A cancelled commission will be marked as cancelled and any payment made in that commission will be 100% refunded to the client.

If you have more questions, don't hesitate to message me!