sell or continue renting

[Brent Rogers]

Does anyone know of a good calculator to analyze holding and renting a property versus selling?  I found one on allpropertymanagement.com that appears to be legit.  However it always returns a verdict towards holding and renting no matter what I input for sales price.  I do this for a five year horizon.  I guess it assumes:

1. you can get later what you can get now or better (it has input for this)

2. if your current returns are high ROI it will always beat a reasonable input for return profits from sale