I haven't "lived" at a school since I was at school myself but I know (or have met) many, many (current) boarding staff - both teaching and non teaching.
As someone above said, you get what you put into it.
Firstly, if it's an idea you think worth considering, it would be sensible to look for vacancies in a school your Dc could attend. You don't have to go with the one your friend has suggested - there are lots!
It's almost certainly harder as amember of the teaching staff - really full on. Your DH might find himself teaching full time + being a house-master + being (moral) tutor to a small group of children as well. The people who do well absolutely love their busy life. You cannot do it if you see the children as a nuisance or resent dedicating 99% of term time to the school.
(You might also get to lead vacation trips - sports, skiing, art history etc anywhere in the world.)
Some spouses take on an auxiliary role in the school and house. Others continue their separate working life elsewhere and only meet the kids in passing. Either is acceptable, depending on the set up of the school. But again - if you're going to resent the children or resent the time your spouse spends on school stuff - it's not for you.
Also, there's a difference between prep and senior schools. Preps are (generally) very touchy, feely; looking after essentially little boys or girls, with all that entails. At senior schools the pupils are expected to be more autonomous, with staff keeping a watchful eye and heading off any problems.
I think if you have the energy it can be fabulous. Please don't do it if you aren't prepared to work to keep children happy.