I am thinking about adding a bungalow to my property....?

I've found a plan for a bungalow which matches the architectural style of my house very well and will add approx. 480 sq ft of living space to the total property. We live in a semi-mature neighborhood with property prices in the 180s to 240s and square footage from 1700 to 3000. Spatially and from a landscaping perspective, the bungalow would work well in my backyard and still leave me a large, gry area for baby #1 (here) and baby #2 (planned) to play in. I'd use the bungalow for an office and guesthouse. The approximate total cost is about $50K. I purchased my house for $146K and it has been appraised at $156K. We've made some very cost-effective, DIY improvements in the home and it is architecturally in line with the higher value homes in the neighborhood. This addition would bring my total living area to approx. 2000 sq ft. My question is...financially, would this addition make sense? All opinions and thoughts would be appreciated!!