What about alternatively going directly to owners of the kinds of businesses you’re targeting? Can be less buyer competition. And you can avoid paying a finder fee or commission.

Carefully review the fine print of any engagement agreement.

PM me if you want to Zoom about this.

Since it is most likely success based upon they bringing you a deal then there is nothing wrong with keeping all options open.
From my personal experience, it is within the range.
For my agreements, I usually negotiate a flat rate but I also allow for concessions deal by deal specific especially if the financials of the deal will be too tight.
for example, we can agree on 5%, but the deal you are working on will only support 3%, then guess what? The commission for that deal is 3%. This is me but I know there are folks that are very rigid and won’t budge. As long as you don’t have an exclusive with this individual, you always want to keep your options open. For a previous deal we were working on, we have 5 separate agreements in place because the first to the table wins. What do we care how many agreements we have in place as long as the deal gets done then everyone wins