I've never heard of paying a 6 month fee in advance.
We do not handle seasonal rentals. However we collect our management fees from tenants rent. If they do not pay. We do not get paid.
We also have a maintenance agreement that gives us authority to take care of repairs that are less than $250. Happy tenants pay their rent on time and renew at a higher rate... less vacancy less cost to the owner. Again these are for long term rentals.