Who owns this house?

[Alex Verdugo]

So I'm looking through the MLS the other day and find this property. Looks interesting for whatever reason, one main house, a trailer and mother-in-law suite. I decide to do a little more research into this property. I see a satellite photo of the property. All three structures on the listing are fairly close together. But I notice something odd.

Theres another building near the back of what I assume is the end of the property.  I go to the county website to see where the property lines end and sure enough, the mystery building is on the property.

The list of questions-

If this mystery building is on the property but not listed in the MLS, would I still be buying it? If not, why not?

Is it possible for the current owner to sell just the structures and not the land underneath? Essentially saying, I'll sell you the building that are on my land.

Is this more common than I think? I'm sure there are mistakes where property lines are changed but not documented properly or someone thought the property was only half the size it really is.

Would all the correct information about the structures on the property come out during the inspection?

And this last one is really just to see how far my options go. Let's say that I buy the three units that are on the listing, including the entire property. The mystery building is now my property, can I refinance the property as a 4 unit property? Can I resell as a quadrupled? Do I have to get the property re certified as a quad?

Has anyone heard of this type of thing happening before?