[Appen] Thoughts on project Amur?

So the afformentioned project popped up in my project list and it is asking for us to advance up to $500 USD which will be fully reimbursed upon sending in our receipts. I've never had a problem with payments from Appen but this seems like a significant amount of trust on our parts. I'm certainly a little hesitant to proceed. Anyone else have this project and what are your thoughts?