When you say that it makes money on a monthly basis, what does that mean? After all expenses (including saving for projected major expenses and maintenance), does it make money? If so, how much?
If you don't know how to accurately figure expenses (again, including escrowing future maintenance), do some reading around here and some googling. This is going to vary based on age of property, type of property (a condo where the HOA does most of the outside maintenance is going to be less than a SFH where it's all on the owner), the age and condition of some of the major parts of the home (appliances, outdoor paint, roof, etc.).
Also, what is your rental market like? Do you foresee rents rising much? How long are places generally vacant?
Also, if you are considering selling, why are you refinancing? If you aren't already committed to that, hold off until you decide whether to keep the place or not.