To build in the backyard or not

[Miguel Ochoa]

Hello all I purchased a home in the east Bay Area with a good size lot 15sqft. I have been looking for deals to flip but my current best option is to build out in the back yard. There is no comps in the area that would support the build out. Rent are still good but I would want to sell and be cash ready. I could build an Inlaw unit save on fee and build out or build a 2 story house and be all in on my cash. What worries me is that if the comps don't come in all my cash will be tied up in the property. Could be a big move I will be attempting the build out my self so it will be a learning experience to do more build outs or add ons. What do you guys think about additions to the back of a house?