It is possible to use
3D as a reference for drawing 2D sprites as well, if that is a viable solution. Personally, I would advise against 3D character art in a visual novel for the reasons mentioned by Mellanthe and SundownKid.
3D tends to look better in motion, and 2D works fine in stills. Take Disney movies for example, because they lean toward 3D nowadays, and compare with a 2D animation like Avatar: The Last Airbender. In Disney movies, notice how things are still moving even when the characters are not doing anything in particular. On the other hand, it seems entirely normal in a show like Avatar for complete stillness to occur between animations.
This is because in real life, motionless things are usually not alive (desks, tables, fruit). Well, plants are an exception, but mammals are entirely different. So when we see 3D in digital media, it often seems as if a character is not living when there is no subtle motion...due to the connection in reality. In 2D, we instinctively understand that it is not a direct emulation of real life by virtue of having only two dimensions, so we do not typically expect constant motion. I hope that made sense.
Just wanted to explain a little rather than just agreeing.
In short, it might be beneficial to loop brief animations for character sprites if you wish to find a 3D artist (this may avoid the uncanny valley noted earlier). It might work better that way, but it is by no means necessary. For objects, well, they are motionless anyway so 3D would work for spaceships and even environments.
Nine Hours, Nine Persons, Nine Doors uses 3D for objects quite well.
I am in favor of finding a 2D artist; however, I feel you should choose what is best for your project.