At some point we will get access to a Auditore villa, which will allow you to collect money from tourism. They are stored in a room on the right of the entrance - in a small chest. 
Money are added every twenty minutes - box has also a maximum limit of gold (depending on the level of you character).
Claudia has a book in which you can check your progress. Here you can read about all elements needed to achieve 100% of the development of your house.  The value of your villa can be raised by renovations of various buildings in the city, development of store and collecting and many others.