These issues are very fact intensive, but generally yes, the odor of marijuana constitutes probable cause for a search. You have greater 4th Amendment Protection in your house than you would in a car or on the street, but the state will likely argue exignent circumstances prevented the police from getting a warrant due to the fact that marijuana could easily be destroyed or gotten rid of during the time they were seeking the warrant. An interesting issue to consider is whether you were in constructive possession of the substance. There is alot of very favorable case law on this issue. Your lawyer should explore all of these issues thoroughly before advising you on how to best proceed.
From what you are saying, yes, he had a right to search the condo.
Unless someone said that it was their weed, however, it's hard to prove whose it is. As the other attorney pointed out, the concept of constructive possession comes into play and may be able to help.
Talk to a local criminal defense attorney. Many, including myself, offer free consultations.
The Law Office of Thomas Almquist
901 NW 8th Ave. Suite C-7
Gainesville, FL 32601