I wouldn’t suggest getting a rabbit from a pet store. The mills they often come from are awful, and not only are you supporting that, but there are also a ton of behavioural issues that go along with coming from that kind of place. I definitely would suggest adopting from a shelter or rescue, as they will often come already spayed/neutered (especially if it is a bun specific rescue) and you’ll get to know what their personality is, meaning you’ll know if you’re a good fit.
As Louie said, they need a minimum of 4 hours of play time a day. So that would be (at least) one 4 hour out-of-cage play session, or two 2 hour out-of-cage play sessions, though more is always better. It’s also best to have play sessions at times when they are active (dawn and dusk) as it really doesn’t do much for them if it’s in their sleeping hours.
As for cage size- I know some people say a minimum of 8 square feet but I would definitely suggest 16 square feet or more. You’d be surprise how small the space starts to become once you fill it with the essentials (litter box, hideouts, food/water bowls, toys, ect.). I’m fostering to adopt a bun soon and I just set up the space the bun is going to have. It’s about 24 square feet, and while it looks quite large while empty, I found it filled up quickly. Make sure not to overstuff their space as well so they have room for lots of binkies and zoomiez. That said, make sure they still have lots to do in those hours while you’re away. Boredom breakers and puzzle toys are great to keep them occupied while only taking a small space in their pen. Edit: You can also scatter feed them their pellets and/or veggies, and if you feed them right before you leave for work, this can help knock of a good 30 minutes of the bun’s alone time.
If you aren’t going to be able to spend much time with the bun (4 hours out of 24 really isn’t all that much) you might want to look into adopting a bonded pair. You can either adopt two single buns to bond, or adopt an already bonded pair from a rescue. If you get two already together make sure they are properly bonded. Whether you get a pair or a single bun, you should definitely get them fixed though. Unspayed females have a huge risk of cancer (the bun I’m planning to adopt had a tumour- luckily they caught it in time and gave her an emergency spay) and unneutered males are known for a nasty habit of spraying amongst other unpleasant behaviours (which female rabbits can exhibit as well).
Gosh, sorry for the essay! I hope this helps answer some of your questions though! 😀