How to go about renovations?

[Chris Ha]

Hi all! 

I was always pondering how to go about the following.

Scenario: Upon purchasing, doing renovations to increase rent OR upon exiting, doing renovations to increase the sale price

1. How do I perform the renovations if I have, say 90% occupancy?
2. Do I evacuate all the units to perform the renovations and provide temporary housing for the tenants?

I always hear we should do renovations after the purchase or before the exit but I never heard the strategy on how to do it.

Thank you!