The study appraised the viability of investing in residential real estate submarket in Lagos State, using the apartments in 1004 Estate as case study with a view to providing a guide for investors and portfolio managers on investment decision-making in Lagos. Lagos, a mega city being a point of attraction to real estate investors makes it necessary to undertake real estate investment performance evaluation. To achieve this, the study ascertained the various risk status of each of the property submarkets and the return strength of the various apartments in 1004 Estate. The study further identified the risk adjusted rate of return of the various apartments in 1004 Estate and also examined the potential of diversifying within residential real estate sub-markets. The study depended largely on secondary sources of information. Data were sourced from the books of the company over a sample period ranging from 2010 to 2017. The data collected were analyzed using descriptive and inferential statistics. The findings show that the risk attached to the various apartments is high and there is strong relationship between the apartments' returns. This implies that the apartments are not fit to be contained in a portfolio. Recommendations from the study are that diversification should be discouraged within a specific real estate submarket as the apartments are usually affected by similar traits.