What do you mean by "realistically?" If you mean that, "realistically, we need some kind of taxes," I suggest you read
this. If you mean that, "realistically, we won't be able to eliminate the income tax," I suggest to you that if we eliminated Social Security (which is more harmful than helpful for the poor anyways) and appropriately reduced the military budget (we'd still spend more than all of our enemies), we could eliminate the income tax and then some. We could easily make up some revenues by eliminating quotas and prohibitive tariffs and replacing them with low, revenue-gathering tariffs.