YES! OMG! That's the one. It was such a nice story. Made me cry a few times.
Yes, it is not on Viki but I watch a few k-dramas on another site called ondramanice.tv
Would you by any chance be able to help me find another k-drama?
I don't remember the main plot and I believe I only remember a few of the episodes. But it has a young girl (maybe in her 20s), her friend gets her a job cleaning an apartment for a guy who is always working and is kind of a loner ( he is not the rich type either, just regular salaryman). He requests that the cleaner is gone by the time he gets home, but one day the girl is still there and she ends up hiding as not to break the rules, but it turns out that the two knew each other.
I am very sorry if this is not a lot to go on. I watched this series 3 years ago and haven't been able to remember what it was called or come across anything similar.