I think you should revise what you're offering, wallet software can't own balances and crypto addresses aren't labeled with whatever wallet name their keys were generated from.
Overall, it's a bad deal. Hope there will be stupid people who are willing to share privatekeys that contains a lot of balance in it.
Not to take sides with either the OP or potential clients, but the OP daringly takes the plunge to front the payment for users who boast a commendable reputation. It's a rather equitable approach, even though a few aspects warrant a second thought before we entrust our wallet to others.
Will go first if you are trusted
However, the unfortunate aspect here is that the OP doesn't furnish a definite proposition concerning the margin awaiting the previous wallet owner. Whether it's rooted in a fixed percentage or pivots on the OP's whim remains undisclosed. For instance, shelling out 10k to receive 11k translates to a 10% margin for the original wallet possessor. But what if the wallet merely houses a modest sum of USD $10? Would it merely culminate in a modest gain of USD $11, or could the outcome potentially exceed that sum?