you may have heard "good fast cheap... pick 2" this is similar.

if your content is dynamic, you have more to worry about. DB servers, storage other application specific issues...

if your content is static or close to it, round robin DNS is plenty. rsync between 2 boxes, and set up the round robin. How far away the boxes are determines how long they take to sync and how much of a safety net it really is. next to each other in the same rack protects from HW fault. different datacenters protects from power and networking. Different states protects from natural disasters.

if you don't know how much to spend then....
you need to figure out how much money downtime (unexpected) costs you. Then you can figure out how much to spend to reduce your chance of tht downtime. If it's going to cost you $1000 per hour, and you expect that with 2 boxes in the same datacenter there might be a 1% chance of failure of both systems that would require 24h to come back up, then your total loss would be 24K, 1% of that is $240 to spend on mitigation. in that case, put your systems in different datacenters. If you're going to lose $100,000/hour, then spend 100x on mitigation.

refusing a lawful order of a police officer is a crime. Refusing the lawful order of a school safety officer (most places these are commissioned police officers) is also a crime.

charge her.

it's not that hard.