Emergency Reserve $

What kind of emergency fund does one have, or have access to for that crazy unforseen event that could happen. I have listened to Frank’s gas line problem on the CD’s and Dave’s storm damaged park. For sake of arguement, let’s assume 100 space park with city services and stable occupancy–no POH’s. Park has working class tenants and is not a war zone. Is there a percentage of gross that one should hold back, or $ amount that one has access to cope with a nasty event? I’m just trying to get a handle on my finances and want to budget appropriate funds for potential purchase. I really don’t want to be one and done. Any insight from the powers that be would be helpful. Thanks, Mark.