A .22 rimfire might be a good place to start if your brother-in-law has limited shooting experience, although you don't say if that's the case. You said he's thinking of getting a varmint rifle rather than target rifle, so I assume there are some critters on his land he needs to trim down, even though he is not a hunter. While a .22 LR is fine for small stuff, a step up to a .22 Magnum is appropriate if the critters he intends to shoot are say fox size. If coyotes are a problem, I'd prefer a centerfire rifle, in which case a CZ 527 in .223 would be a nice walking varmint rifle.
If the ranges are short to medium, a fixed 6X compact scope will work, although a variable like a 4-12X has certain advantages. If he leaves it set on 12X though, chances are he'll miss shots on critters that are moving or at close range.
