making a duplex, into a big house?

[Jonathan Beemer]

Hi BP, 
just a random question for future investment ideas and options.
say i purchase a duplex in a neighborhood for 120K together. the neighborhood is mixed with single family homes and duplexes. would it be better to combine the 2 units into 1? making it a single family home. or keep it as a duplex and sell it?
this is if i wanted to sell it for sure and not rent.
just wanted to know if you can make more money selling single family homes or duplexes?