Experience with fees for a buy-side broker?

Hi!

I am running a search (single sponser, focused on education in the US) and I am currently evaluating working with a highly regarded buy side broker. He is offering two types of payment:
1) A monthly retainer, and then a success fee (% dependent on the transaction amount, but the retainer fee DOES NOT get discounted from the success fee)
2) A flat fee to be paid within 12 months if there is not a transaction, or a higher flat fee if there is a transaction.

The amounts make sense to me (especially given other posts I have been reading here) but I am wondering:

- Besides the obvious pro / cons and risk up/down side here, is there anything you see that favors one scheme versus the other?

- For the first option, how long does the retainer payment usually go up until (until what stage in the deal)? And any advice on how I might ensure that the deal will is not prolonged for longer than necessary (given that there is no real incentive to do it quicker)?

- Are broker fees normally added to the deal costs or are they part of the search costs?

Thank you!

Daniella