Well any tax question is going to be very hard to answer as tax laws vary from state to state, and country to country.

Generally however, you have to pay taxes if you're earning morning. Usually there is a threshold however, meaning that you need to earn over a certain amount before it's taxable.

As for trademarking....a registered trademark is an R. TM can be used at anytime, but will not be valid if someone actually registers it, and as for the costs, EEight has you covered.