My guess is you do not own rentals and you are not knowledgeable about real estate investing. A multi-family property that costs $1.1M should produce close to $22,000 in gross per month to be really profitable. One that rents for $6,000 is a guaranteed cash flow negative property. You will, over time, feed this alligator a couple thousand dollars a month in expenses. It looks like taxes and insurance might in the mortgage payment, but you have not allowed for any other expenses. Vacancy and collection loss, utilities you pay, repairs and maintenance (including tenant turnover), capital improvements, etc all need to be deducted.
This is a situation where leverage can kill you. Both your house and the triples will have mortgages with high payments. Lose your job, have a tenant file bankruptcy, almost anything could bring down this house of cards. There is some good information on evaluating rental property in the real estate thread. Please take a look at that before you go any further. Pick up the book that Sword Guy recommends. I would not touch this property.