Up until recently 100% financing was available on up to a 4 unit investment property by means of an 80/20 Mortgage. Due to the new credit enviroment the guidelines have changed dramatically.
Please realize I am an expert in invesmtent property financing and have been doing this for over a decade. Currently on a two unit or Single Family investment property we are financing up to 90% of the cost. On a three unit property, 80%, and a four unit 75%. Once you get 5 units you are now in commercial loan territory and you can finance up to 90% again with less than favorable rates.
I would suggest putting more money down, the more units you purchase. This allows you to maximize cash flow by not paying a higher interest rate on a higher risk loan. If you have any more questions or need details, feel free to contact me.