How Leasing Brokers are Paid

[Will F.]

I was wondering how leasing brokers are paid based on finding a commercial tenant for retail/restaurant space?

I'm trying to figure out if I should go the commercial broker route in listing some nice, hip retail spaces. I was also contemplating just listing them myself and throwing them up on loopnet/costar/MLS etc and just test the market

I've heard 6% commission is paid on total rents for the length of the lease term-- but is that capped and is that total amount paid upfront on lease signing?  I mean for instance if I sign a lease at $4500 a month for a 5 year lease that is $4500 rent x 12 mo x 5 years = $16,200.
It seems like a lot if for instance the tenant breaks the lease 6 months into the lease for example.  

Are there standard or common clauses or anything I can put in the Listing Agreement to guarantee I would be able to pay reduced commission based on uncertainties with certain potential tenants?