I bought a new boat with a saildrive. I was REALLY hesitant. Make SURE you add in a galvanic isolator, they are cheap. I have an SD50 with a Max-Prop, I like the setup. I am still getting used to the idea of a big hunk of metal down there. I burned through my first set of anodes in four months. I have a meter to check my hull potential that I religiously do on a monthly basis and chart the results.
Corrosion Reference Electrode
You need to keep your hull potential between -950 to -1100 mV.
Additionally, here is a link to the Yanmar Service Advisory regarding their saildrives.
You will also "learn" how to change lube of the drive while in the water, not hard, but an interesting activity.