I would recommend reaching out to the owner well in advance to ask for check-in instructions because she doesn't send them out in advance and they are not uploaded on the listing. I spent the last hour of our drive trying to get ahold of the owner so we wouldn't be locked out (Hint - if you contact VRBO they will give you the owner's phone number). After calling, leaving a VM, texting, messaging on VRBO, and contacting the VRBO helpline (who reached out to her too), we got a copy/pasted message with the door code from her. When we arrived (over an hour after check-in time) the cleaning lady was still vacuuming our unit, so I suspect they forgot we were coming in the first place. The cleaning lady was very sweet though and finished up quickly once we got there. (And, according to earlier reviews, it seems we are not the first people who have run into this situation).
Also, the shower had maybe 30 seconds of hot water per shower before it turned cold - not ideal after two long days of hiking.
Aside from those two things, the apartment was fine, nothing special. The best part was that it was located above an awesome coffee shop/breakfast place that had really good food and they were really fast. We went there all 3 days and it was great. I would say that Hot Springs overall is not the best place to base out of when visiting the Black Hills, we had to do a lot of driving. It's an hour from Custer, and almost 2 hours to get to Deadwood and Spearfish. Next time, I would stay somewhere further north, more central.
BUT - if you do stay in or near Hot Springs, make sure to make a reservation at Buffalo Dreamer for dinner. It's a tiny, fine dining restaurant with exceptional food and the staff is wonderful. Highlight of our stay.