Honestly, if they're willing to do the art before you pay, that's... very trusting of them? I see a lot of artists getting scammed out of payment for art they've already done, and subsequently asking for at least partial payment up front. Technically they're the one taking a risk, not you
That said, they have ~180 watchers, and their name doesn't autofill in google - probably they're not a particularly well-known artist. If you're that worried, I'd suggest contacting a user who's commissioned them in the past and asking if they'd recommend them.