I agree that maintaining a multifamily home long distance can present a challenge. You need to speak to a few real estate agents to determine what its worth in today's market. How soon are you looking to relocate? Do you need a quick sale?
Would the property appeal to investors or owner occupants? Sometimes the price of the home will determine if its an ideal property for investors or owner occupants. Will the rent of both units cover the entire mortgage and taxes? If yes, it may appeal to an investor. If the rent from both units doesn't cover the expenses, it may appeal to an owner occupant, who, like you, can live in one unit and rent out the other thus the rent helps them to pay the mortgage.
Another thing to consider regarding is are your current tenants on a lease? If yes, when does that lease expire? A new owner will be bound to the terms of your current lease and some buyers want to buy a multifamily home without tenants so they can live in both floors (extended families or find their own tenatns) and some buyers look to buy a home already with tenants especially if they need the rent to qualify for the mortgage.
I grew up in Belleville by #8 school and know the area very well. Two family homes range in price from the mid $200,000's to the low $400,000's. If you are relocating quickly, I wouldn't suggest overpricing the home nor will an overpriced home attract investors. The home should be well priced and agressively marketed. Feel free to contact me to discuss the sale of your home.