2-4 Family: A property that has 2 to 4 units in it is considered residential real estate.  If you plan on purchasing a multi-family that is 2-4 units and the intention is use it as your residence then you will be able to obtain conventional interest rates on your mortgage.

If you are planning on purchasing a 2-4 units property as an investment it is considered a residential investment and the interest rate is normally 1 1/4 to 2 1/2 % higher compared to the home being used as your residence.  The difference in interest rate primarily will be affected by credit.

5 Units and Above: Any property that has 5 units and above is not considered residential real estate.  Very often 2 homes are on one lot that consists of 5 or more units.  In all cases the interest rate will be higher as a totally different group of lenders would be used for this purpose.