It all depends. Here you do not need a license to lease property and therefore many property managers do not offer commission or referrals.
Unfortunately, I'd have to advise you NOT to expect a commission but do you best to protect yourself. The prior advice is good and should help.
No set structure for leasing commissions when they are offered. Sometimes its a percentage of the total lease dollars, sometimes its a flat fee, sometimes its a structured payment, like 5% of the first year, 4% of the second year, 3% of the third year, etc.
Jan 16, 2009