Question on Converting SFR into a Duplex

[Chris Reyes]

Hello BP community,  

I’m helping orchestrate converting my parents rental property into a duplex and would like some insight since this is the first time attempting this. 

Background: 
The house is in a smaller town in Colorado. Population: 8200 (and growing rapidly). 

Lot size: 9,365 

House size: 760sqft (2bed 1 bath)

Zoned: R2 for Duplex 

Owned Free and Clear 

Possibly have to fix foundation

I have already contacted an architect to give me an idea about pricing but I had a few questions before I send him info. 

1) how do I determine what size I would want the duplex to be. 
- based on other duplexes around?

- based on how many rooms wanted?

- based on the size of the lot?

- all the above? 

Any advice or suggestions about anything to do with converting a house into a duplex would be much appreciated!

Respectfully,

Chris Reyes