Do you see used Fastrack for sale now and then? My small layout will need the smaller 36" curves to climb up to the upper deck. In the long run I think it will be easier to have a nicer looking layout as I won’t have to do any ballast work.
Fast track is a pretty new product. I don’t think there is a lot of used track around yet. Good luck on your layout.
Ebay seems to be a good place for this as folks buy the sets and do not need the track.