Our picks for open houses to see this week alternate between unlikely luxury from humble beginnings and faded glories of previous eras with potential for future greatness. They include a renovated Greenpoint wood-frame townhouse with vinyl siding, a late Victorian brick three-family in Bed Stuy with some fanciful details, an eclectic two-family Renaissance Revival brownstone in Bushwick that historic-detail fetishists dream of, and a circa 1900 pale brick barrel-fronted two-family that’s essentially move-in ready. Prices range from $1.095 million to $2.75 million.