to put it frankly, it doesn't really matter what people think about the idea. what matters is if the city will allow you to do that. you've already reasoned that subdividing a lot to create 3 homes is better than building 1 by the powers of basic math. anyone that tells you that if you can pull that off is a bad idea or does not compute, must have a different calculator... or a broken one.
what matters most and is the only answer you need to first seek is what the city will permit. if your question is more along the lines of pitfalls and finding out what questions you don't know to ask about subdividing a lot, i'm sure the bp community can give you all kinds of scenarios. and again, the city would be a good resource to guide you to their city ordinances on what they will allow.
for what it's worth... what you have in mind is a good idea... maybe. and a bad idea... maybe. :) definitely easier to ask the bp community, but better first to start with the city. afterall, they're the ones that will enable or disable your idea, not any one person's 2cents on this forum - mine included.
good luck!
