They also make supurb second homes and by the way, if it qualifies a your second home, loan interest, county license/registration fees are tax deductable. If you rent it out, all maintenance, insurance expense as well as depreciation may also be tax deductable. Boats, live aboards and floating homes can qualify as second homes.
A lot of people are not aware that there might be alternative living available in Tiburon with the opportunity to live "on the water" for a fraction of the price of a home in Tiburon.
I guess I found your question too late, Perhaps you have already bought the one Mario mentioned below. If not, the least expenseive one I see in Tiburon today is priced at $1,125,000; it/s a 3/2, 1174sf house. The next one is priced at $1,399K.
But why stop there if you are looking for properties in excellent towns with great schools to purchase and invest? I know a lot of excellent schools in Marin. Ross, kentfield, Mill Valley all have wonderful schools. Some more distant (from the City) towns like San Rafael and Novato also have excellent schools and great investments. Take a look at http://www.sylviaSellsMarin.com/MarinAPI and let me know if you are interested in any of the areas and we can go from there.