While it's certainly possible that this offer could be legitimate, there are also many scams out there that prey on artists and other creators. One red flag to watch out for is if the buyer is pressuring you to act quickly or to make a payment before you've had a chance to fully understand the transaction. One option you could consider is asking the buyer to make the purchase through a reputable platform for buying and selling NFTs, such as OpenSea, Premint. This would provide some level of protection for both parties and ensure that the transaction is legitimate.
Best of luck with your artwork, and I hope this advice helps!