Do it before you move *anything* into the house.
It's fairly hard work and very, very dusty.
You know how fit you are, whether you can lift the machine around etc (30Kg-ish). If you have respiratory problems or significant back problems, you might want to give it a miss.
Otherwise it's not particularly demanding on skill, but to get a high standard of finish does require you to be meticulous - retract every nail, secure anything that's loose, repair any damaged boards *before you start sanding* and then get all the dust out before you start varnishing.
One person can completely sand 2 rooms a day, including all the edging
- if you're less meticulous, and really go for it, maybe double that.