I'm working on a fantasy novel and seeking to buy cover art.

Subject matter: A modern young man is mysteriously sent to a tropical island chain where he gets powerful stone-shaping magic. He gets involved in a small-scale civil war, then deals with foreign explorers looking to claim and colonize the place, hoping to reap the benefits and avoid the worst aspects of that.
Image ideas:
-A beach scene with someone doing magic involving floating stones or water. Could be the male hero, or a vaguely Polynesian tribal woman; natives have otter-like ears and tails but otherwise look human. (This is the "put attractive woman on the cover" option.)
-Hovering cube of stone, one or more faces showing tropical seas, islands, and ruins.
-Beach scene with a flag stuck in the sand. Flag shows a triangular design of elemental earth/water/wind. Something in the scene indicates magical stuff happening, such as a mystic circle glow around the flag base.
Overall the picture should convey "this is a fantasy story involving elemental magic, tropical islands, and maybe colonization".

Format: Image size 1875x2850, lossless PNG or high-quality JPG, 300 dpi.
Time frame: Would like it done within around 2 months.
Rights: Need rights to commercial use for a physical and digital book cover, and to post the work to advertise the book, and to transform/edit the work (add title &c., possibly modify for banner ads &c in only digital form), and technically to copy/redistribute it as part of selling the book. Do not need rights for physical merchandise besides a book.
AI allowed?: Prefer not, but allowed, only with written guarantee you have the legal right to give me the rights listed above.

Other:
-Needs substantial room at top and bottom for title ("Shaper of Isles") and byline; I can do the lettering myself but if you're good at it we can talk about that.
-Can pay half up front, half when done. Check, Paypal, or Boosty available.
-Would like to see WIP and approve it.

I would specify what license/rights I want or need.

I would even explicitly mention that I need commercial rights because I'm publishing. (Seems redundant, but I've seen people advertise covers without commercial rights.)
And specify whether you want human-only or will accept hybrid or AI art.

Do you want sole rights to use the art?
Do you want to be able to manipulate the art? (Cut it down or a part out to make banner ads.)
Do you want to be able to make promotional material from it? (Use it on a website, make a print poster for your table at a con?)
Do you want to be able to make goods for sale from it? (Mugs, posters, pins?)

Good points; I've modified my post to address them.

Cool. Be aware (not a lawyer), with AI art, you cannot copyright the art. You can copyright the arrangement (not sure of the legal term) - like the exact book cover, the combination of text on the art.

And if you combine pieces of AI art, the combination can be copyright, but the individual components are not.

Here's my portfolio, affordable prices, sketches and WIPs for feedback will be provided. PM me if interested.

Hi there!
I would love to make that art

Here's my portfolio for your review: https://www.artstation.com/giovannipedroni

Hello, not sure if you are still looking for an artist, but I'm interested.
You can look at my art here https://valkyart.carrd.co/#portfolio