Q. Any red flags to look for regarding cost reimbursements (mailings, etc.) in case they try to make money that way?
A: As a refresher for everyone, you never want to pay agents money upfront to represent you. The only money you should every pay an agent are small amounts so that they can reimburse costs for mailing and postage. Keep in mind that they are simply recouping costs, not making any money off you. Concerning how much money you will pay for mailing costs, etc., when you sign a contract with an agent, this should all be spelled out. For example: “The agent has the ability to collect up to $50 per month in mailing and postage costs as part of reimbursement. Itemized receipts available upon request.”
To answer your question about red flags, not really. It seems silly to try and scam writers out of a few dollars here and there to actually turn out a livable profit. If any agents out there are scamming writers, they are plenty of people complaining about them on the Internet - trying to warn you. Much more common would be bigger requests. A scammer agent may ask you to pay $800 upfront for editing and submission costs, but promises nothing in return.
Nickel and dimed. I'm sure you got it...