Renovation on a rental house before or after we move back -- Tax Advantage?

[Mike Huggins]

We have a second home that is currently being rented out.  With no owner occupied, house is worn more and also needs to be updated due to be dated.  We are 19 months from moving back to this second home full time.

From what I understand, we cannot perform a renovation and move back in immediately and claim the renovation as an expense/depreciation.  
In order to take advantage of the tax situation we must show that we have a renter in the house after the renovation.  Right?  How long do they need to stay in the house?  3, 6, 12 months?

Anyone else run into a similar situation?  What did you do?