Licensed Realtor in NJ and GA
Cash only means just that. It means you may not purchase a house using a mortgage you must have the entire purchase price in cash.
This often happens with the bank owned properties, or homes at need total rehabilitation.
Sometimes it's just an estate sale where the seller just doesn't want to take the contract when a mortgage is involved.
Just as a side note the link you posted is for home that was already sold. Please feel free to give me a call at 908-675-0167 or email me at firstname.lastname@example.org and I can answer some more questions for you to help you understand what's involved and perhaps help you find a home.