Paperwork is the process that assigns property shares under your possession. Every place you buy will have to go through this. The larger the property and bigger the number of shares, the longer this phase will take. You can always automatically complete this, by using coins (no worries, there are many ways to get them!)
Tip: While in paperwork, the property does not generate income, but you still have to pay maintenance costs.
Caution: If you're buying more shares of the same property, the whole object ceases to bring income – not only the part you've just bought.