This is a common problem for preparers that get random clients from who knows where, lots of people looking to scam you...you give them a copy and they never return and never pay you and use your numbers in some DIY program.

Many preparers collect a deposit up front prior to starting the preparation, just to make sure you dont end up working for free.

If therye going to make this an issue, and refuse to pay, Id return their workpapers back to them and they can go find someone else.  I wouldn't give them a copy until I was paid for my work.