There's no way of expecting them to move out if you're unwilling to help pay any of the initial expenses of moving out. They don't have their own income and they can't even get a job - 15 miles to town is simply not a walkable distance on a daily basis. As impatient as you may be to make them move out, you have to be reasonable.

Besides this, your callousness is really quite appalling. You brought your children into this world and you have a responsibility to them - from what you replied on another comment you say that they complain and cry that you've isolated them; well, unless it was their choice to be homeschooled, the isolation technically was of your doing, and they are justified to feel estranged and isolated, especially since they are teenagers and teenagers tend to derive a lot of importance from having non-familial relationships and friendships.

Do reconsider your attitude towards them and your own moral and parental responsibilities, and at least give them a financial headstart if you want them to move out immediately. You can perhaps consider it your last substantial investment into raising your kids.