Alexandre, by 970 you mean the GEFORCE GTX970? That is an old GPU and not good for daggerhashimoto (ethash). To mine ethash you should have a RX570/580. But even with that and a modified GPU at the moment you can achieve only about 1 USD per day for 1 card.... On any other algorithm like cryptonight or equihash it will be even less. particularly with one GTX970.
Even a dollar a day per piece is also hard nowadays, the projections of the hash rate per day is too small and if you are in the place where
electricity bill is really huge, better not to mine for the meantime or if you are doing this for future goal better to reassess your mining hash
before proceeding, its too difficult to earned you have to take the risk if you believe and you can wait till the coin value will go up.