Invest BTC in btc trading and you get a good circle going on 
Yeah, I think thats the safest option that he can have.Invest into BTC and trade if you dont have time to do that then invest into a mining farm or set one up yourself if you get cheap electricity at or around your place. You will need a lot of cooling equipment along with the rigs though. Could be expensive on the whole.A lot of capital needed for that mining thing.
BTC to BTC or the other way "altcoins"
Have done some research just now and I see a lot of people are really getting hooked with it. I see that the only part you will be doing is monitoring each price which could make you a little busy. I suggest making a list in an excel form or anything where you could write the best altcoin here which have a lot of movement too.