Hack a Duplex and Build on Property?

[Stephen Ward]

We just sold our first home for a happy profit, and we are trying to do our first hack by buying a Duplex to live in for a year with a 5% down conventional loan.  We also have property and are going to be building a house within the next year.  

The Questions:  After the year is up, will we be able to go 5% down again on building our new house, while we are still holding the debt of the first duplex?

Will the passive income we start receiving (once our vacant side is filled) help with getting our new home loan?

Thanks!