Again, it depends on several factors. Many companies offer additional amounts to get the tattoo done all by yourself.
Many companies also have their own tattoo artists and their own setup to get it done. So, it is better if you can talk to the end client and clear all your doubts.
If you are using platforms like Fiverr or LeaseYourBody, you can also mention the payment terms beforehand.
Even if you get these offers from any other platforms, you should talk to the company representative to know who will pay for the tattoo.
If you think that the tattoo cost will be included in the final offering, double-check the actual amount you are getting after spending the tattoo cost.