Hi Monica,
Welcome to Bigger Pockets! It is all relative. Whether a particular ROI is worth the investment will vary from investor to investor depending on what other alternatives investment vehicles are available, how management intensive the investment may be, and perceived risk.
11.9% ROI for a real estate investment (in general) is fairly decent considering stock market returns generally average 8% to 10%. Now if you're wondering if 11.9% is a good return relative to other multi-family properties, you should consider characteristics such as location (how likely is the property going to appreciate compared to your other alternative properties), tenant quality (are the tenants going to be troublesome or pay on time), how far is the property from you (I like to be able to drive by once in awhile), how marketable are the units for your area (general risk to your income stream, 3-bedrooms and 4-bedrooms generally take longer to fill compared to 2-bedrooms during turnover; hopefully you're in a family-oriented area), etc.
I hope this gives you a better idea of how to determine if the ROI is satisfactory enough to pull the trigger.
-James