I have the opportunnity to rent an antminer s7 for 200€ forma three mmonths. Given that I dont pay for electricity; Would it be profitable?
Flat out, yes that is profitable assuming 200 Euro (~$225) is a one time cost for 3 months of operation (even accounting for extreme difficulty increases), and also assuming it comes with a PSU (or you have one on hand to handle ~1500 watts).
However, you may state that
you don't pay for electricity, but I imagine someone else does. Think they'd notice their monthly electric bill increasing by about 1,000 kWh?