It can be anywhere from 0-20% for the most part, on average you are looking at 10% of the house value, obviously the more you put down the lower your payments. And like it was stated earlier you also have to pay closing costs. And if you don’t mind buying in Schenectady be ready to throw down another $5-7K for closing.
General rule of thumb for what you can afford as a mortgage is usually 3 times your annual income.
I’m not a realtor or anything so I can’t give exacts, however I did take a Real World Math course last semester where we spent a lot of time on mortgages and house buying.