How many years would a bank finance on an investment property?

I found several duplexes in my area that are around 20k. I have the 30% to put down but not the full 20k. Would a bank finance this as a mortgage and if so for how many years? I would like to put the mortgage on 5 or 10 years. I am hoping to obtain just a conventional mortgage. Would the interest rates be higher since it's will be used as an investment property?