Time for ROI on Capital Project

[David Ware]

Is there a general rule / thought on incurring capital costs and the time it takes for a return. I am looking at converting a 1 bedroom to a 2. If the cost is 7,500 and I would get 100 more per month (6+ years of rent to break even) does that make sense? What time frame do you look at for the cost to be returned?