Only buy if you're willing to accept a +50% loss. You never know when it's going to happen, and if you're asking here you probably don't have a clue either.
Don't buy if you have things pending like debt, strong family commitments.
Remember that this is a "risk" investment and well it has to be money you can't count on in case of an emergency.
I'd only buy if you're willing to accept a 100% loss, don't use money that you have a need for right now. This is a risky investment still but this is all my opinion, do your own research.
I was talking about 50% because of the drop we had recently, but as far as the risk of losing 100% I think it's almost zero, the only way is to get it to 0, and there are still a lot of decimals from 0.1 to 0
p.s: Although I'm not insinuating that I'm bearish against the price of Bitcoin.
Bitcoin is a highly volatile investment, only invest what you can afford to loose. As others have mentioned if you have pending debts take care of those first and whatever is left over dump into what you see fit. To answer the wallet question, if you're an investor get a paper wallet. Put that wallet in a safe place and then get an app/program to put that wallet in "watch only" mode. This way if the device gets lost or stolen your coins are still safe.