Best ROI studio, 1 bed or 2 bed?

[Julie Petersen]

I'm looking at single family homes to rehab and want to as part of the rehab create a separate space (or two!) to rent out to help offset the mortgage. I'm wondering if anyone knows which size additions make the most sense? For example, is it better to add two small studios as opposed to 2/1 or large 1 bedroom or 2/2. Just wondering in terms of cost to build, which size makes the most sense in terms of ROI. I'm looking in the Portola and Bayview neighborhood areas.