Thats about 7 months ROI (using 36/day) which seems about right at the current going rate. I would test each rig before hand to ensure everything works.  Depending on the internals you may be able to build your rig cheaper. Depends on what PSU, CPU, RAM that he is using. You may be better off piecing yours together and then building it yourself. Make sure you take into account the electric cost you are paying and update that in whattomine as well as ensuring you have enough power at home to plug all these in.