Seller is trying to back out of wholesale deal — What do?

[Mark Beekman]

[State of PA]

I have a real estate wholesale deal under contract (fully executed purchase agreement), but the seller is now saying that they think they can get more money, so they’re not going to sell to me. Ideally, I’d like to cloud the title of the property to prevent a sale to someone else. Would a Notice of Interest/Memorandum of Contract do the trick? If so, is there a boilerplate form that I can simply fill out and file myself? Or, do I need to hire an attorney to file a lawsuit and then a lis pendens?