You can't put in a granite countertop, add a deck or redo the bathroom for $3,164, but you can make an investment in your home that adds more resale value than any of those changes. According to Remodeling Magazine's latest Cost. vs. Value Report, the only home improvement that gives a homeowner back his or her entire investment in resale value is swapping out existing front, back and side doors with steel doors. This may challenge your aesthetic sense and seem minor at best, but the average $1,218 spent swapping out an old door and jambs with a 20-gauge steel door with new casings and lock set consistently adds $1,243 (or 102% of its cost) in resale value. You can spend $2,436 adding $2,496 in value to your home and still have more than $700 left over to either save or spend on a toy worth locking behind those new doors.