To do's and don'ts of commissioning a freelancer?

[MagicBuns]

Hiya guys,

I've been considering commissioning an artist for the visual novel I'm making, but I seem to be doing a bad job at it. I want to be able to find an artist who could slowly with me over time, as I'm on a budget myself. I am clueless when it comes to the dos and don't of this situation, or what it's like as an artist for hire, but at the same time, I don't want to be ripped off.

Please could someone help point me in the right direction! D:

Thankyou!