I would suggest , if you are not willing to spend money, to ditch incandescant and at least get yourself some cfl's or shop lights they are cheap and work . A regular bulb may grow a plant, but if you get some cfl's maybe even a metal halide(doesn't have to called a grow light to work) look up gymnasium lighting on ebay those 400 watt mh with a cone style reflector will wolrk well they usually run 65-75 dollars shipped. If this is beyond your budget go to walmart and get the spiral cfl bulbs at least 26 watt the 42's work good but are a little more pricey. these are sufficient they will grow and flower a plant good luck. I reccomend dropping $135 on the cheap 400 watt hps at htgsupply.com you WILL get your money's worth first harvest. I wouldn't even bother with the incandescant light. good luck