eviction

The new owners will probably handle this.

Give this "renter" the information that the building has been sold and he/she must deal with the new owner.

In which case, there are going to be problems with the new owners if this situation has not been properly disclosed. Kind of like I sell you a second hand car, and after the sale is complete, I mention that my old war buddy is driving it in another state. You own it, and are free to chase it down.

Was the person in the garage served with a formal eviction notice? It's a matter for the sheriff if so.

No legal lease is mentioned.

This could be a tresspassing issue if the new owners mean business.

I wonder why someone would purchase a building and not know what was going on inside of it.

Hope the fella finds a new place, soon.