The amount of the downpayment will be determined by the type of financing you are receiving. Most first time buyers are using FHA or CHFA which currently requires a minimum of 3 1/2% deposit. Do you fall into this category of buyer? Feel free to contact me with additional questions.
Long Answer: Depending on the type of loan you get for a property, you can put anywhere from zero money down, to about 20%.
CT's Housing and Finance (CHFA) offers loans starting at 0% down
The Federal Government offers FHA loans starting at 3.5% down
Most banks offer conventional loans with 20% down (but I've seen 10% and 5% first time buyer programs from banks offering conventional loans)
I'm a full time real estate agent in the area and I'd be happy to help you look into financing options. Feel free to contact me directly at 203-815-9118 or Scott@CTProperty.com