Way to get an early start! Trust me... it still won't be enough time. In order:
1. From a realtor's perspective, a 2-3 month lease agreement is a waste of time. Considering the amount of paperwork, negotiating and legal wrangling required for a large scale lease, their return on investment for a short period is not enough to justify the footwork. But, the average retail store size is just over 10K feet, so maybe you could find a recently closed spot in a mall or busy area that needs to fill a slot temporarily. Can't hurt to ask!
2. Loan officers typically love businesses with tried and true business plans in industries with rock solid reputations, and guaranteed potential. Unfortunately, haunted houses do not fit these criteria. At least in my experience, it can be exceedingly difficult... but others here might have more insight than I.
3. As far as security goes, you can not go wrong with hiring off-duty police officers. They usually charge a reasonable amount ($20/hr here), their presence can be a huge deterrent to potential troublemakers (guns and tasers and cuffs, oh my), and the local PD will be much more willing to help you out if their own people are onsite. Keep a couple on hand, with their squad cars out front. The end!
Best of luck!
I became insane, with long intervals of horrible sanity.