Hello there! Thank you for the ask, its a fun one to consider!!! I'll make a bulleted list!!! LONG POST INCOMING!!!!! Some of these ideas I think could be "in general" a part of the lives of "tiny/fairy people" in media too!!! But some of these are Borrowers specific! I hope you enjoy!!!! ~!

I think if they are close to houses or are born/raised in houses, they would probably prefer that strictly "borrowing" lifestyle generally. Having said that, ough it's fun to imagine what they'd do if they were farming! Or even living in proximity to a garden/farm and what they'd choose to Borrow there! If they had to borrow from a human farm/garden, basil has so, so many leaves! I have a basil plant, and I can say that I probably would not even notice if one leaf was taken, and that alone could probably last them a week if they were careful! Even things like cherry tomatoes and strawberries, when they grow enough I can't keep track! With something more prominent like a kale plant, I would definitely notice, so I'd assume they would likely have to avoid plants like that to avoid getting caught or mimic how a worm would carve out parts of the leaves so its indiscernible as to who "ate" the plant. If they had to grow their own plants, though, I think they would opt for something where every part of the plant is edible. For example, the entirety of a beet plant can be eaten for the most part, so for that in particular I'd assume they would pick the greens until the plant is near dead, then dig up the bulb when they can get no more from the plant.

As for other places borrowers can live besides human houses, I think they'd know how to use the most durable materials in their respective environments which to build their own houses with, where to build them, and how to disguise them from humans or otherwise make them look like no big deal. That's kind of simple, I suppose, but fascinating to me, that Borrowers could have "region-based" house designs, like how humans around the world in different environments learned to build shelters that best protected them from their given environments (SEE: Pagoda designs in Japan, the fact that those have lasted for HUNDREDS of years is such a testament to how well designed they are for such a mountainous and earthquake prone region, they're remarkable to see in-person and it's remarkable to think how HUMANS made them with WOOD!!!!), but, like... In a smaller radius if that makes sense. If you're a human and you like, walk 10 miles, you could see a lot of cool and unique architectural work... If you knew what you were looking for, that is.

Sort of related to the above two, I would wonder if the "grass is always greener on the other side" mindset would apply to house borrowers and not-house borrowers. I guess we get that in the Book with Arrietty, but I really want to see the reverse scenario where a non-house borrower would think living in a house would be cool.