Discovering unit demand in a market

[Duane Ward]

We're getting ready to close on our first investment property. Theres an opportunity to expand the one of the units in the duplex. What are some good resources to understand what people may be after more in that particular market in a rental? 

ex: the apt is a 1bd 1ba that we're debating on expanding into a 2 or 3 bd 1ba. This would take away from the other unit which is 5bd 3 ba converting it to a 4 or 3bd 3ba. 

Essentially trying to understand what people moving into the area may be seeking so we know if it's worth the dollars spent to go for the extra bedroom.