@Elisa-Gonzalez-O-Magaña
Hello! I sometimes do contract work like this.
When working with a larger company, I've always been asked for just an hourly rate, not a total price for the work. Sometimes they will ask for an estimate of time, but that is after they detail for you what exactly is expected. For example, if they need 5 or 20 characters, or if they need designs and poses etc. Also, they know it is an estimate, not a guaranteed amount.
When estimating the time I always tell them MORE time than I think it'll take, that way I am finishing things faster than they expected and I'm not stressed for time. This makes us both happy!
To give you an idea, in my area (San Francisco, California) $30 an hour would be a cheap rate.
For small companies or independent people, I would make them detail out for me exactly what is needed so I can gauge the amount of work, estimate higher than I think it'll take and then times that by the hourly rate I would like. I would detail in my contract how many revisions they are allowed to ask for, and then an hourly rate if more revisions are requested on top. I would also specify partial payment upfront and at the end, and what happens if they cancel but you've done a lot of the work already. I would also ensure images are allowed to be used in my portfolio after
the product launch.
Do not do any work without a contract or a written agreement - ever!