I’d point out where all the stuff was and (if I were around), jump in to work also. – I have dogs and a cat, so my house always needs cleaning, no matter what day of the week it is.
Personally, I wouldn’t like it. We have someone come in and clean, but the day before she comes we clean up stuff we do not want her to deal with.
A neighbor has a key to my house, so if I have to work a long day, he can go over, let the dogs out to potty, feed them, give them a little attention. I’m mindful on days that I expect to work late and make sure the place is reasonably picked-up.
I obviously like and trust this neighbor. But in the unlikely event that he took it upon himself to, say, do my dishes, or clean the bathroom, I would be absolutely horrified. Again, it’s all about the relationship.
Personally, I’d be thrilled. But it’s a tricky situation. I think you should stick to only cleaning stuff that you can be expected to have used yourself, so that any cleaning would look like “I cleaned up after myself” and not “You’re a slob, bye!”
Kitchen clean up, because you’re staying there and you may have fixed something to eat. Launder the bedding you used and leave it nicely folded. Bathroom cleaning is okay, too. Maybe even run a vacuum around the living room, but dusting or washing windows is right out.
If the visitor was a good friend (the kind I would give my key to, and let them stay without me being there), and they’re volunteering to clean or arrange for cleaning, I’d be quite happy. My house always needs cleaning, so they’d be right.
I voted grateful and delighted. Rodgers01, can you come to my house next? You can stay as long as you like 
I am generally against it because it seems invasive and judgy about the way the person keeps the house.
Weirdly, my mom does this at my house but I’ve mentally gotten over it because she’s not going to stop, so I chalk it up to her neurotic behavior and general mom-ness. Anyone else, I would be offended.
But with the additional information you provided about your visit, I’d be okay with your cleaning only to the extent that you are cleaning up after yourself (dishes washed and sink cleaned, for example) but no farther.
I agree with asking her first. I would be offended if someone cleaned my house, but if they were staying with me it wouldn’t need cleaning. Someone less uptight than me might appreciate a cleaning, but definitely make sure it’s ok first.
Heck, I even hate cleaning people cleaning my house.
Kitchen cleanup is typically a safe area, provided you can figure out where things are stored; if you can’t guess where she keeps the really weird cooking utensil, just leave it on a clean towel and let her know you had no clue where’d she want it. A bathtub swipe and clean, no problem, I mean, you used it, right? Dusting is good, 'cause nobody likes doing that, and heck, she might not even notice it, even if you do. Anything else, enh. I am in this position at the moment, staying with my in-laws. I practically BEG her to let me do stuff, but this is a longer-term stay and not just a few nights. But this is my helping with daily and regular messes, not a huge cleaning or anything.
Actually, I might suggest sweeping and mopping the floors: she might not even notice right away but you’ll feel better 
And that’s something that takes some time, which you have more of right now than she does, it sounds like.
I voted Guilty.
A friend house-sat for me once for a couple weeks. The house was just fine when he came over – no dirty dishes or garbage or clutter, clean bathrooms, etc. When I got back, the living room carpet looked really nice. I asked him what he had done, and he said “I just vacuumed the hell out of it”. It made me feel like a bad housekeeper. It also made me change the way I vacuumed. Who knew that one pass wasn’t enough?
I’d go ahead and wipe down counters and clean the sinks and toilets, mop and vacuum, but I wouldn’t do anything more than that. Those are things you can do that she might not even notice. If she doesn’t notice when things aren’t clean, maybe she won’t notice that they’re clean, and you’ll be more comfortable staying there.
I picked uncomfortable, both because of privacy and because I can be a bit picky about how things get done. I’d really prefer to do it myself, thanks.
I think the only time it’s appropriate to clean someone else’s house is when they are unable to clean it themselves to their usual standards, e.g. due to an illness or bereavement, etc.
I could use some new friends. Does this person do wallpaper?
As to the op. You could wash dishes or vacuum the rug as a generic thank you but other than that, no.
Giving someone a clean house is like giving someone a houseplant: there’s this unstated expectation that they will take care of it, and a huge potential for bad feeling when they inevitably don’t. Non-slobs look at a slobby house and think “Poor thing. She’s just so far behind, she’s overwhelmed. I’ll get this good and clean, and then she can maintain it”. They think this because it would be true if THEIR house looked like that, which is why their house never looks like that. If I wanted a clean house enough to maintain it, I would have done it in the first place.
So while your friend might enjoy a clean house, if she’s like me it means she can’t ever invite you back, because she won’t want you to see how she “wasted” your gift by retrashing the place. And be honest, if you came back in six weeks and it was like you’d never cleaned up at all, wouldn’t you feel a bit miffed?
My ex comes started comming over and cleaning my house several years ago. She has broken several very expensive objects while trying to clean them. She has washed shirts that I only dry clean, thrown things away she figures I don’t need etc. One time she tossed all my t spoons because she figured I didn’t use them, I never eat with tablespoons excet maybe soup. I think she may have recently accidentaly thrown away my brand new camera. I am afraid to say anything because she falls apart at the slightest hint of critisism.
I would say common area only and don’t throw anything away!
I don’t keep an especially clean house, but if I’m having house guests, I will do a fairly thorough cleaning before they arrive. If there’s something I missed, I would be embarrassed that someone found it and cleaned it. The exception is when my mom comes. She is both welcome and encouraged to clean (which she does) and I am delighted and grateful.
If the host had made it clear that they hadn’t prepared properly for your visit and they apologize profusely for the messiness, then I think cleaning up would be fine because the host has owned up to the slobbery.
But most people do clean up before guests arrive. So cleaning up after them would be saying that their efforts weren’t good enough for your standards. Of course, their sloppiness could be indicative of them not considering you worthy enough. But this is not a foregone conclusion. Some people (meekly raises hand) simply do not see all the dustbunnies.
And also, some people may think your friendship is SO close that they don’t have to sweat the dustbunnies. I’m also guilty of this too. I’ll break my back cleaning the house for strangers and for my parents, but maybe not work so hard when it comes to my sister. Because I figure that she loves me so much that she won’t care if things are a wreck.
I for one would do a happy dance if a friend of mine did some housework for me. Particularly as a surprise; there’s nothing nicer than opening the door to a clean and tidy home, and it means that I don’t have to do it. YAY!
Only you know your friend, Rodgers01 - I think if they’re happy for you to stay a few days while they’re away, I imagine you know each other well enough for your gesture to not be misconstrued.
I agree that cleaning up upon arrival for a brief visit is rude or at least Not Nice.
However, in the OP’s case, he’s been there several days – long enough to contribute to messes – and will be there several days without the host being there at all prior to the time when the cleaning is done. I see it more as just cleaning up after yourself really well, than “correcting” any error or omission.
But as many have said, there’s no one right answer, its all about knowing your friend.
If I had a house guest that I knew well enough to let them stay in my home while I was gone for a few days, I wouldn’t mind if they tidied up a bit before they left. For me, personally, the house would have been pretty darn clean before they got there.