Leaving our oversized master bedroom for a triple bunk bed for the kids, and the sitting room space (divided by a privacy curtain) for us to sleep. 

Even with this prices, some triple deckers in the areas you mentioned still positively cash flow while smaller single condos may run at at a loss, depending on the terms.

But based on the city records, the plot is zoned to allow it already (obviously would triple check that with someone in the zoning office before converting anything), the zoning regulations explicitly specify that plots with that zoning can do multi-family without any special allowances (I believe "of right" was the phrase used).If it is already zoned to allow either, is it still possible for the city to say, "Hey, I know we said you didn't have to ask for special permission to do multi-family here, but we really would rather you keep it as a single unit."?

We would love to be able to rent a 3br home on a triple corner lot for the next 10 years while we wait to build.

No to real estate investment for the timebeing for me at least ( temporary)Because I already invested and I want to see how the market is doing, I want to learn more, networking.I am against real estate gurus who says invest in big amount and leave your job bla bla bpa, first when you invest in big amount and you do have cash the interest rate will be huge and this decrease your profit and yield/ cap , also high yield mean high risk second real estate as any business have good time and bad time so leaving your sustainable job and depends mainly on real estate investment is quite risky method, if one could generate double or triple his income real estate this is something else, I don't think typical person could rich quickly without high risk

Purchased my first triple decker from a family member when I was 21, then 5-6 years later I purchased a 6 family.

This is once again for all of the new members that join this site specifically in the New Jersey and Pennsylvania areas.  95% of the people on this forum are here to help but triple check everything. 

Getting a crappy health insurance plan, or underpaying your income taxes, to increase your "net" income on each pay-check isn't actually a pay raise, since when you get sick now your deductible just tripled, and your April income tax bill went up as well!

In the attached report of the subdivision called Prestonwood, in the last year, sales have been cut in half, and listings have tripled.

Looking at this tax law, I'm thinking of selling another house that has tripled in value and using the capital gains from that house to fund the construction of the 2nd unit.