Okay, you've got a location, and props, and scenarios, and insurance, so now you need the all-important part: the actors. Actors who get into the story are the ones who make a haunted house successful; they engage the guests in ways that mere props alone cannot.
However, finding such wonderful people is a difficult task, especially at prices you can afford. Serious actors know their worth, and a person who is just going through the motions— actors call it "phoning it in"— hammers home the unreality to the guest. Someone who is obviously bored makes a haunted house boring.
How do you get good actors, then?
First of all, expect to audition far more people than you actually use. If you can't bring in enough people to have a choice, you will have a problem. (An exception is if you are part of a theater group who is voluntarily putting on a haunted house, because everyone involved will be acting their hearts out for the house to succeed.)
Secondly, you will have to consider whether volunteers are worth the price. Sometimes a group of apathetic volunteers is more costly in the long run than paid actors. If your house is boring or unenthusiastic, the all-important repeat business simply does not happen.
Thirdly, a large number of the people who want to work in a haunted house will be minors. This can be problematic. Check the labor laws for your area to make sure that any underage employees are properly taken care of in terms of hours, breaks, permits, and pay scale. You may also want to limit their participation to areas where they cannot be cornered by belligerent guests.
And, sad to say, many minors are unaware of the demands of working in a haunted house and absenteeism is common. Carefully screen to make sure you hire reliable teenagers. They do exist, no matter what you think.
Good places to look for haunted house talent are the local community theater groups and colleges. If you can find an improv group, that's gold. Also consider people who have done such things as work at summer camp or who have worked with small children, as they are used to infusing everyday activities with enthusiasm.
As for payment, remember that you get what you pay for. A community haunted house can get away with pizza and sodas as payment, but a professional operation should certainly be paying at least minimum wage, and probably a good bit above that. Haunted houses should be fun for all involved, and because there are hazards that most guests never see, the pay should reflect that.
Next up: Props