Thanks everyone for the valuable inputs.
So at Hashnest I will deposit BTC and then go to shop and purchase an S5 for example, one S5 is 1TH/s equivalent.
Wait for 3 days and watch my wallet? That's it?
That's one option; the other tab for "Market" allows to to buy/sell shares of S3, S4, S5 on the open market. They'll be in your acct as soon as you buy them so no waiting for 3 days. Many times the shop price is cheaper than the exchange price for S5, but you wait 3 days.
S2/UMISOO, S3, S4 shares are cheaper than S5 shares. They also don't make as much BTC per day due to maint., but there's some good trading to be had on those markets.
Lots of options at Hashnest.