@Alice-F-R In the same kind of situation, I have just written up my own contract with specifics about how and when you will be compensated. You could request payment per illustration page, or by hour. Just a fair warning about requesting payment per illustration, some difficult clients may try and request a lot of revisions, which could end up de-valuing your time significantly, but you can get around that by capping the number of revisions.
I have done this in the past where I provide rough sketches throughout the process, then I require a partial payment as I go. I will then provide watermarked final illustrations and wait until I'm paid in full before removing the watermarks and sending the completed work.
The agreement doesn't have to be anything complicated. Just do some research to make sure they are legit, and make sure you come to an agreement that is going to protect yourself and your time.
@Alice-F-R I usually send them my rates, then never hear from them again 
There are a few good self-published authors out there, but most are pretty amateur and don't realize how much time/effort it takes to make illustrations so they haven't prepared a reasonable budget and cannot afford it. I'd suggest to ask a few questions about the project including her budget, and don't get your hopes up. Most of these things never get off the ground. But it's good practice!
Hello!
Outside of the contract stuff, here are a few things I would think about:
Has this person published before? If so, in what market and was it self published or via a publisher?
With self publishing, what is the plan to distribute, sell and manage the book process? Over the years, lots of folks have reached out to work on a book but precisely just ONE had any plan on HOW to sell them. Most just saw I had a large following on Instagram and though that was enough.
Everyone will have a differing opinion on this one--if you want to so a sample illustration--fine! Any additional work will definitely require a contract, plan, scoping session, etc.
Also: If it feels like a scam...it is. No harm in ever walking away.
Anthony
@jvartandillustration Thanks for your reply! That’s a great tip with the watermarked illustrations. Would you provide a free „sample“ illustration or start straight away with the contract? I asked about timeline and budget but she has ignored that aspect in her response…
And how do you do it with the partial payment during the process - is that something that you have in your contract as well? Sorry for all the follow-up questions! It’s really helpful getting other peoples insights into this 
@NessIllustration Thanks for your thoughts! These are really helpful tips - I have asked about timeline and budget but received no response, only a request for a sample illustration… I’ll try getting some more information. Next time I‘ll know what to ask straight away. Thanks again!
@AnthonyWheeler Thank you for your response! These are some great things to consider and I think I definitely need to ask her some more questions. Thanks again for your thoughts!
I would send her a jpg of a sample you’ve already done with a similar amount of work,detail etc and let her know how long it took and your fee so she gets an idea of rates you expect. I have created character sketches in pencil for a prospective client prior to getting a job.
@Alice-F-R Apologies for the late response. I guess in your position, I would wait until she is responsive when it comes to timeline and budget. I usually don't provide anything for free, but I suppose if you need some clarification about what they are asking for in terms of object placement, you could draw some really rough sketches. Your time is valuable, so just don't let yourself be taken advantage of is my overall point here.
I worked with an author earlier this year. He agreed to pay me half when I delivered a full sketch, and the remaining balance with the finished artwork. If you wanted to protect yourself more because of a relationship that is untested, you could certainly break up the commission payments into more segments. Hope that helps.
@Larue thank you for the tip!
@jvartandillustration thanks for the tip! I like the idea of splitting the payment. And good to be reminded to not let yourself be taken advantage of. She hasn’t responded to my question about timeline or budget, so I’m assuming it won’t go further. But it was an interesting learning experience as I’ve never been in this position before
I would send her a jpg of a sample you’ve already done with a similar amount of work,detail etc and let her know how long it took and your fee so she gets an idea of rates you expect. I have created character sketches in pencil for a prospective client prior to getting a job.
