Examples of fixes:
I now play without the "resort towers", but keep the lots (just changed to normal community lots):
Some objects are below ground level: Spa/Bistro Rabbithole at 10 Sunshine Street, Sparkling Sands at 45 Paradise Road, and La Costa Verde Resort at 75 Fiesta Circle. (You should also be able to spot the darker shrubs and trees that were placed below ground level and move them above ground. You can view them in the basement level.)
Loner - Solitude (It has no door! The house is on stilts and there is a ladder going inside.)
I added a ground floor with front and rear entrances and moved the main living downstairs.
Modern Folly Makeover had no complete fence and required Sims to go upstairs to visit. I expanded the downstairs from the simple bar and bath.
http://www.thesims3.com/assetDetail.html?assetId=8571687
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/085/716/87/roof_up_original.jpg
Check for stacked spiral stairs (which can cause route failure). Use ladders or delete top floors. Check blocked showers/baths or tubs turned wrong: Los Amigos house, Rubisel Ichtaca's boat, & Floating Fortress, docked at Pleasing Port (unoccupied). Also, check for homes with arches as entrances that look pretty, but keep everybody but family from the door. Easiest fix is to delete the arch and that part of the wall. You can also just extend the house, as I did for the Collins - Colonial Casa - 76 Civic Center (The front door is set incorrectly and they have problems accessing the top floor, so delete access to top floor. The toddler will get stuck in the space by the front door. I extend the living room so there is no porch.)
The house on the right of the Collins green one is the Vidals - The Painted Lady - 74 Civic Center (It has a small fenced & cluttered yard and outdoor stairs leading to a bedroom. I delete the stairs, enlarge the house, & add spiral stairs.)
(Empty) - Modern Marvel - 10 Modern Mile (no front door set, very unlevel terrain, & stacked stairs) I uploaded a fixed version, if you want to replace it.
http://www.thesims3.com/assetDetail.html?assetId=8565894
It has a separate post below.
Babes on the Beach - Holiday House - 25 Riviera Road (Sims often get stuck in the tiny flat space behind the entrance foundation. Flatten ground around (or expand) front deck, move stairs to right so paper will be delivered closer, & smooth incline to mailbox.)
It has a post below right now too.
Again, I deleted old PhotoBucket pics. (Beware of free sites that might decide to charge later and have a back up plan!)