(an extremely silly retelling of an old-ish riddle)
So, you've just come into possession of a haunted house. Well, not possession, you're not a ghost, and the house isn't actually haunted anymore. It was haunted, but the ghosts have been... relocated. Let's not worry about the morality of the situation or how exactly you own this house now. Point is, you've now got to go through the house and work out how to make it somewhat livable for the living again.
It's a pretty old house (not sure why you'd expect otherwise, considering how it is (I mean, was) haunted), and a big thing that stands out to you is the electrical work. Absolutely none of the fixtures have been updated in a long time: it's all vaguely dangerous-looking ceiling fans and incandescent lightbulbs that might only still work because they were made before planned obsolescence was a thing. And though everything miraculously turns on, the switches are really confusing! Nothing's labeled, and plenty of fixtures are activated by switches in inconvenient locations - some of them are even in completely different rooms of the house. Also, all of the analog clocks in the house are set to the exact time, down to the second, and you can't work out how to adjust any of them. It's weird.
The weirdest thing about this house, though, has to be the infinite basement. You don't know the specifics on how, exactly, the ghostbusters never got back to you on that, but you do know that the basement definitely seems to be infinitely long. Relevant to your job is that there's a lot of stuff in here. An infinite basement means an infinite storage area, and the previous occupants used it to its' fullest potential - or, technically, a finite fraction of its infinite potential, so actually 0% of it. They've collected a lot of things. All completely unorganised, mostly junk, some valuable, some haunted, some both. Of course, the house isn't haunted anymore, but the stuff, on the other hand...
You want to go through and catalog this stuff so you can work out what to do with it all. Based on the floor plans (which are thankfully finite in length and terminate with a "..."), the basement is split into three parallel aisles, each of which is lit by a single infinitely long row of suspended lightbulbs. Because running an infinite row of lights is pretty expensive, you decide to go through the basement one aisle at a time so you don't need to light it more than necessary. Sure, you could just use a torch... but it's the spooky basement of a formerly-haunted house! You don't want to go down there in the dark! You're also superstitious that the row on the left has the most haunted stuff in it (the ghosts were big fans of Latin and wordplay), so you'd like to start with the right-most aisle and go left from there after finishing it.
To this end, you need to turn on one row of lights at a time. Inconveniently, the dodgy wiring poses a problem: you know which three switches (in the master bedroom) activate the lights in the basement, but not what row which switch activates. You're sure they're completely reliable, that each switch only controls one row, and that each switch is definitely on when in the downwards position, you're just not sure, for each switch, which row lights up when it's turned on. You want to work this out, and you want to be 100% sure about it, so you can proceed in your one-row-at-a-time thing without leaving anything up to chance. Oh, and the basement is at the bottom of an infinitely long flight of stairs. You can't see the lights in the basement from the top of the stairs (because they're infinitely long), and climbing them is pretty difficult so you want to avoid doing it as much as possible. Jumping down only takes like, a few seconds, though. This is definitely not how infinity is supposed to work, but you decide not to worry about it too much.
You think about the lights, and you know you can work out which switch switches which in just two trips, but then you'd need to climb up the infinite stairs twice. Can you do it in only one trip, and how?