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What coins actually you want to mine maybe I can give you some idea if what wallet would be the best, And could you tell us if what are available devices of your friend?
I might just tell him to get Coinomi beta setup on his iphone. It's the best solution anyway.
Cheers
Just in case you want to pursue nicehash, then I guess what you need to worry is the history of its security breach, and also its TOS citing that they are not already liable on any future hacks
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The good thing is you can freely transfer your BTC funds to Coinbase free of charge.
Yep, it would work, been done that when I need a fund to simulate NH's cloud mining, pointing out some of my rigs from MPH pool