Not sure if I understand correctly. Say I buy coin from Coinbase / Localbitcoins. If I want to move what I just bought into another wallet, it will be charged?
I also heard when you buy, in general the buy price is about 3% higher than market price. Same when you sell. This mean if I trade at 6% higher, it will only be breakeven minus the fee (unless I keep them in the online exchange wallet)?
Another question is, if I want to keep coins in H/W wallet for safety, I have to consider fee and the time for transaction confirmation which is tired to the fee. If there is a big drop and gain, everyone wants to do the same, the time will take longer even if you choose fast transaction.
I can answer part of your questions. If you use Coinbase to buy Bitcoins, they will charge a fee. I dont know what the current fee is, but I think it would be more than the miners fees because Coinbase makes a profit from these transactions. If you move the coins off of Coinbase, I dont remember if Coinbase charges a fee, but most likely they do.
If you want to trade Bitcoins like a day trader, dont use Coinbase for this. You can move your Bitcoins to an exchange like Bittrex where they do day trading quickly and with a much lower fee than Coinbase. These trades will be very low fee like 0.15% (varies from exchange to exchange). The fees are almost insignificant because the transactions are being done on the exchange.