If your concerns base on time and space you should see the "one or two?" question under this aspects:
If you want to give your rabbits the space for a real rabbit life, you can imagine 6 square meter (approx. 7 square yards) for one or two rabbits (there is no difference here, because two rabbits could be socialized very well, and can life "close" together).
Indoor this means a little room, or part of a little room. (If you now ask "there are so nice little cages, why 6!! square meters?" I want to imagine you this: rabbits can reach speed of 60 km/h (approx. 37.3 mph) and love it to run. Think about rabbits more like about cats than mice.)
Additional they need daily access for minimum 8 hours to a big and interesting area, like your entire apartment, or the garden (for outdoor rabbits look on this question: How do I ensure the safety and good health of my outdoor rabbit?).
For the afford of making this area save for your rabbits, it is not important, if you have one or two.
(And if you choose the "nice buyable cages" because you are a child (and the parents do own the money and the power), or it is really really not possible an other way (like in a shelter with comparatively small space), then you should buy this one for two rabbits have space in it, because the smaller "for one rabbit" is to small anyway...)
(I assume you think about the daily/weekly needs of your rabbits, because they affects your all-day-life more like monthly/yearly events, like the visit to the vet)
If you have rabbits you need time for feeding and cleaning. This times do not change between one or two rabbits.
The time that would change is this: If you have one rabbit, you have to be the "official" partner of this one. You have to groom it, interact with it and entertain it the whole day (and night: rabbits are active day and night, they rest no longer than 2 hours at once).
If you have two rabbits, they groom, entertain and "talk" among themselves. You can "visit" them whenever you have time, they will be happy about any interaction. But you know also your bunnies are lucky if you are at work, or sometimes in holidays (with rabbit sitter).
You can do all the things, you want to do with the rabbits in your free time, but you have no sorrow about the health of your rabbits if you have to "cancel one rabbit meeting".
If you have time for one rabbit, you have time for two. And your rabbit will choose a second rabbit, if you ask it.
So in conclusion:
Space afford do not differ between one or two rabbits.
Time afford will be higher for one rabbit, than for two.
If you want to minimize time and space afford, you have to choose two rabbits than one.