what do you advice me to buy ? used maybe? what to consider , is s9 so old it wont be profitable in 2 years (not sure it would even be atm...)
For used machines, you could also talk with Grace/
Minerexpert there are a few reputable members here who have done deals with them with no problems, for US there is also
kaboom pretty solid seller.
Anyhow, 7.5 cents per kwh and S9s is really a bad idea.
Right now, you know it, you're looking at at least one year of ROI if you manage to get a really good deal on some units, but the difficulty is not going to stay the same and the big guys have orders for tens of exashash for the year.
The sad part, I can tell you a lot of things to not do at the moment but I would refrain from recommending gear at this point. Not with these prices.