As per BITMAIN Antminer S9 Review:

https://www.buybitcoinworldwide.com/mining/hardware/antminer-s9/PROS:

- Highest Hashrate: 14 TH/S

- Efficient @ 0.1J per GH/S

CONS:

Cost: $2,100 (price may vary depends on your location and with the current fork)

Power supply are sold separately: $170 - $200 (Additional to your cost)

Base on this site calculator:

https://www.cryptocompare.comHASHING POWER: 14 TH/S

POWER CONSUMPTION (W): 1293

COST PER KW//S ($): 0.12

PROFIT PER DAY: $14.18

PROFIT PER WEEK: $99.27

PROFIT PER MONTH: $425.45

PROFIT PER YEAR: $5,176.36

The above calculations are merely estimated as there are factors which will change the calculations above. Factors are the cost of S9 and electric cost. You may also include the maintenance and miscellaneous expenses that are related in building an Antminer S9 rig.

Now, let's assume that you have already built a rig and the total cost + expenses: $2,500. Then let's again assume that the electric cost stated above is the same in your location. You will ROI: $2,500(COST + EXPENSES) / $425 (PROFIT PER MONTH) = 5.87 (6 MOS.)