To [member=40772]Holmz[/member] point, it depends a lot on your available network of connections. My old dad made a couple of dolls houses for nieces and people saw .. talked .. instant demand!!
Next thing to consider is your setup .. breadboards, etc can be easy with the right tools, or a challenge with the wrong ones.
Something as simple as number templates for house numbers with a creative finish (mdf and some spray paint) could even earn a few bucks if you have a suitable scrollsaw or bandsaw, etc.