Guess for the cost of the engineer or the work? An engineer $1500-$2000. Work impossible to tell, to location and home specific.

By corner, you don't mean the actual corner of the original house needs to be removed do you? If it's a 6 ft opening in a wall next to the old exterior corner, you don't need an engineer to tell you what the header should be.

Be prepared for what might be in the wall. It could be empty, or it could have electrical, plumbing, and/or venting that you would have to figure out how to re-route.

Thanks for the responses! To clear up the questions:

Yes, was just wondering a cost estimate of what an engineer might charge for a consultation, not any of the construction costs.

And no, we wouldn’t be removing the corner—the opening would only be in one wall. But I’ve read that you shouldn’t put a patio door within 4 feet of the corner of a house. This opening definitely would be, so I was concerned it wasn’t as straightforward as a regular opening. We’ve installed an exterior door before and are comfortable with the general process, but aren’t sure what additional considerations there might be. We always thought the addition put on in the 60s that houses the bathroom was a square including the pantry, bathroom and bedroom. But now we’re realizing it must have been shaped more like the state of Oklahoma, with the bathroom being the panhandle and the pantry being the north or Texas, and part of the existing house. Why they chose to build on a bathroom that is only 55” wide is a mystery to me!