Florida does have an adverse possession law, but it requires that you pay the taxes, apparently for seven years. I haven't, because all of the paper work that was recorded was correct. It was only the stakes in the ground that were wrong, although the surveyor did give me an updated copy of my survey that shows both buildings in the wrong location (50 feet from the property line instead of the actual 10').
I interviewed lawyers this morning and hired one. They are going to research everything and present a list of options with an estimated cost and chance of success. Their costs will be all mine, unless we sue and prevail and get a judge to include costs in the judgement, and then actually get the judgement paid. This sounds like a very expensive PIA to me.
The good news is my septic company will remove the tanik for $650, and then I can get a small sump and pump to connect the guest house to my main house septic system for about $1000. The only catch there is I may have to increase the size of the drain field, which would be much more money. At least I would end up with a really big pile of fill dirt, which around here is like gold.
After that, I might be able to get a 40' variance for the building location, and a 40' utility easement. Welcome to the neighborhood, don't mind the transformer in your front yard! I'm still really upset about the new location of the lot line, and can't help but feel it is going to kill my resale value.
John