Around here a portable building, one not built on a permanent foundation or slab, but one which may be fastened to the ground with dead-men or screw anchors to prevent it from blowing away, don't require building permits and aren't taxed. The kicker is that skid mounted portable buildings can be moved short distances by dragging and long distances by being winched onto the back of a flatbed.

An acquaintance lives next the the river and he has a guest cottage and storage shed out back near the river. Very picturesque and convenient to be able to pretty much paddle right up to the guest cottage and fish the river from the back porch. Of course being in Florida when the rains or hurricane comes the river rises. So he unbolts the tie-downs, backs up his tractor and drags them to higher ground on his property. In the last five years he has done it twice.

If and when he sells the property he can take the buildings with him. Handy that.