Here are some examples of how I redo a port that had a family and houseboat:
Mrs. Scott might have been made pregnant with Rubisel Ichtaca's baby some way that causes issues. Evict the Scotts. Bulldoze their houseboat. Bulldoze the houseboat base.
Cntl/Shift/C:testingcheatsenabled true, enablelotlocking on, click on Port, click on padlock to unlock.
Change to residential. Use hammer to delete port connection and port walkway.
Cntl/Shift/C: enablelotlocking off, testingcheatsenabled false.
Delete extra fencing, flooring, and "port".
I leave a port house and simply make it into a cheap starter house.
Perilous Place becomes a pink and turquoise shack on the water's edge:
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/15/roof_up_original.jpg
http://www.thesims3.com/assetDetail.html?assetId=8620815
Delete the trees in the way of getting to the door. Delete the stairs and level land in front of building a bit higher making a level area two tiles wide. Add stairs again holding alt when placing to avoid sinking land. Use terrain smoothing tool to create a routeable path that is not so sloped.
You can place houseboat sims into other homes on land, hoping that moving them resets their issues and you can relocate some sims into the starter homes.
I now have a bunch of starter houses of varying sizes on the ports that had buildings on them.
They are so quick to just add a few things to what is already there.
Picturesque Place - with 3/4 bath and awesome views:
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/21/roof_up_original.jpg
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/21/l0wu_original.jpg
http://www.thesims3.com/assetDetail.html?assetId=8620821
Prosperous pad - with a full-sized bath complete with tub:
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/20/roof_up_original.jpg
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/20/l0wd_original.jpg
http://www.thesims3.com/assetDetail.html?assetId=8620820
Popular Pad - wooden shack with motorcycle and all in one bath:
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/12/roof_up_original.jpg
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/12/l0wd_original.jpg
http://www.thesims3.com/assetDetail.html?assetId=8620812
Pleasing Pad - complete with a real shower and toilet:
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/16/roof_up_original.jpg
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/16/l0wd_original.jpg
http://www.thesims3.com/assetDetail.html?assetId=8620816