Before I would spend a nickel, I would talk to all of your local authorities. Even if your property is zoned Agricultural, around here you still need a special permit to hold an event. In many of the communities around the Detroit area they have really cracked down on all codes and have stopped others from opening. They can hit you with things like easements and access to the event for fire and rescue etc.. Others have stopped corn mazes because the corn might burn and wanted everything outside sprayed with fire retardant. Yes it is stupid but if the authorities don’t want you to open they will find a way to stop you.
I would also suggest talking to all of the authorities, city, county, fire, building, etc… We tried to open a haunt a few years back and received the ok from all but the building inspector which my partner said he had spoke to and got the ok but he did not and they came out and shut us down cold.
It’s good to hear you have done your homework on haunting but have you worked at any haunts? If not, I would suggest working at a local haunt for a while too. It is very, very hard work and you can learn a lot from busting your hump at a haunt for awhile. Even if you think the local haunts suck you can still learn a lot from them. Find out what works and what does not, etc..
Just a couple of thoughts, hope it helps and good luck!