microbrew startup

I wanted to ask...how many barrels per year and tanks would I need to effectively produce three taps available for sale in a "nano" brewery year around?

Also, what space would be needed to produce these results?

How much do new tanks cost vs used tanks?

Do I need different types of tanks for different brews?

The best research is to travel to established breweries and ask them to take a tour. While on the tour, ask them questions.

No way to answer this with the information you gave. There are too many variables. For example:

What type of beer do you plan to brew? (This affects the length of time the beer will be in tanks, conditioned, etc)
How good will your beer be? (This affects how many people will want to drink it and thus the amount needed to keep it on tap)
How good are you at marketing? (see above)
Do you plan to sell off premises? (see above)

That being said, in Washington, D.C. a couple of new breweries have popped up. One has a 10 bbl system and initially had three or four fermenters. They distribute kegs to bars across the city and they are having trouble keeping up with demand.