I would not recommend giving out the unflattened source file at all. There are no benefits and and a lot of risks to you as an artist.
For me (as an artist), I wouldn't entertain the idea of giving a source file and I don't even give full res / un-watermarked WIPS (I also don't know any other artists who would do this but I guess to each their own).
Luckily I have only had one person be difficult about getting watermarked WIPS but they still only get smaller watermarked WIPS like everyone else.
Personally I think asking for source files is a huge red flag and I would be pretty likely to turn down a commission from someone who does that, and would definitely turn them away if they think they have the right to edit the art in any way that wasn't discussed.
no subject
For me (as an artist), I wouldn't entertain the idea of giving a source file and I don't even give full res / un-watermarked WIPS (I also don't know any other artists who would do this but I guess to each their own).
Luckily I have only had one person be difficult about getting watermarked WIPS but they still only get smaller watermarked WIPS like everyone else.
Personally I think asking for source files is a huge red flag and I would be pretty likely to turn down a commission from someone who does that, and would definitely turn them away if they think they have the right to edit the art in any way that wasn't discussed.